C# 10 and . NET 6 for Absolute Beginners

1. Introduction: Welcome to the course, C-sharp and dotnet six for absolute beginners. I'm your instructor for Vaughan Williams. I've been teaching programming for the past ten years. In this course, you will learn to use our programming for desktop applications. These lessons assume no prior knowledge of programming or the C-sharp language, and we'll have you up and running in no time. We will learn C-sharp syntax, variables, loops, and this is on statements, collections like this sender raise loops and decisions statements and object oriented programming. By the end of this course, you will also learn how to add your solution to a source bunch of Management System like GitHub. Developers with knowledge of the dotnet framework and the C-sharp language are in very high demand in this field. This course is chock-full of development tips and it is very beginner friendly and will equip you to be unemployable dotnet developer in any organization. Without further ado. I am happy to have you on this journey and I can't wait for us to start having so fun. 2. Install Visual Studio 2022 Community Edition: Hey guys. In this lesson we'll be installing Visual Studio 2022, which ships with dotnet six, which is the fastest dotnet yet. So to get started, we just need to go over to Visual Studio.Microsoft.com slash downloads. And then we will go ahead and hit the free download on the community edition, which will then give us an installer. Once you run that installer, we will be able to select the workloads that we want. No workloads really referred to the libraries or to supporting libraries for the type of app that you're interested in creating. In this case, we definitely want to get that web development ESP, dotnet and web development workload. But then if you are interested in other technologies, you can go ahead and select them. So you can see I have several workloads selected with a 0 development, NodeJS and desktop development. You can go ahead and split those also. I think that they will come in handy with other projects that you might end up building all in all, once you have done that, you can go ahead and hit Install, which would be done by the bottom right-hand corner. Of course, the more workloads you select is the bigger the download size. So once you've completed that, then you can continue. No one that download is finished, you may get certain options that I am not going to get because I already have it installed. So I'll just walk you through what do we expect? You may get an option where you get to choose your theme. As you can see, I'm using the dark theme, but then you do have the option of a light theme, a blue theme. And the thing is that Visual Studio 22 has many more themes than its predecessors. So even if you don't want to light the initial themes, you can get other themes if you need them. Also, you may be prompted to sign in if you already have 2019 installed on your machine and you are just installed in 2022, you already signed in 2019, then it probably won't prompt you to sign in again. However, if this is your first installation of Visual Studio, you may be prompted to sign in or create a live account, which point you would want to just use your Microsoft issued live at all. Look at hotmail.com at cones, or you can just go ahead and create one. And if my memory serves regard, you can use an another non-Microsoft email address secretes a level college. If I go ahead and create a new project and do a new console app, C Sharp console up. Then this is just going to be VS 2222 demo. All right, go ahead, hit next. Cc is the same thing, but here I can choose which framework and I can now choose the latest dotnet six.net five was released last year and it's according to 1.93.1, sit as long-term support. So it's still quite capable and each one is actually backwards compatible. So five, most of what you're doing, three most, if not all of what you do in 3.1 is still compatible with five. Most, if not all of what you would've done with these two can be forward, forward it to dotnet 6.1. It's sort of supports. I would suggest if you have any UPS stealing 2.1 to start looking to upgrade or update them. Or at least if you're just learning.net Core, don't start with 2.1. When we go ahead and hit Create. Another thing I take note of, I Pause the video. It wasn't really that quick, but I paused the video. One thing I took note of is the fact that it is much fossa, that is probably because it is not a 64-bit application, so it's making better use of your 64 bit machines resources than previous versions would have. No, you're going to see FASTA search times, faster project load times. You have solutions with 109 projects. It shouldn't take as long to load them up. So another thing that I went to point out is that this is a console app. And if you have any experience writing typically C-sharp obligation and you wouldn't know that there is a standard template where you have a bunch of using statements at the top. And then you have int main Java class, and then you have int main, and then you have the code in there. But here all I'm seeing is the code. This is dotnet 66 actually got rid of that whole template. So let me just add dotnet F5 console app project quickly. Let me just call this one demo. I'm at five so we know Next. And then this one is done at five. So that is what we're probably accustomed to when we look at a dotnet five project are done addFive console project or code file. You have your class, you'll have your static void main, and then you have your code. However, in dotnet six, they got rid of the rappers, our own olive that the just start writing code. This isn't, this is not a C-sharp tutorial. I'm just pointing out the two nuances. My C-sharp tutorial, I will definitely go through all of that and the differences between the dotnet, regular dotnet C-sharp and what dotnet six brings to the table. But it's really cool As far as I see it. Now another cool feature to me is it's increased intelligence when it comes to code hinting, hinting what you might be getting its while you're writing your code. Again, see this as a huge productivity when they adopt the feature in tele code. And you'll see that little icon down here that's allows you to kind of toggle some of the options. So if I type console, you'll see that it's kind of auto completing dot write line. It's not waiting for me to go into the list and then select it. I can disperse tab and then tub, as long as they are agreed. Characters to the right of the cursor, I can press tab and then it will just fill them in. I am here. Let me try something else. If I do something like varname, var num one is equal to and then see it's suggesting that I probably want to initialize it to 0. Let me see if it's really that the intelligent, okay, It's suggesting num2. What if I wanted var name? What would it suggest var name? And then a space and then okay, So I guess I broke it. But you can see what it's getting at maybe. All right. So I guess var name is vague. As, you know, you need to type for it to know what exactly walk ten of variable it's going to be before you give the value. So if I said string name one, Let's see what it would suggest. Stringy and one. And also just showing, alright, so that's a feature I guess that overtime it will increase in its offering because this is really based on cold completions, based on other code samples from various repositories all over the place. So I guess random variable names that I desired rarely used, which is probably why it's having such a hard time understanding what I'm I'm getting at. But then he can't see with the num one, num two, if figured it out. I've just press Enter. It's suggesting console dot write line, tab. And then it's going to suggest in the one tab right there, I just printed num one without writing a code line of code and look at this, I press stop once and I'm printing num2. So I think you use it, it will seem easier, it will make better suggestions. It's clearly contextual because he knows that num1 and num2 are in the documents are in the program, knows that he can suggest it later. Don't for my operations. 3. Create Your First C# Console Project: Welcome back guys. In this lesson, we're going to be taking a quick tour off Visual Studio 2022 while we're setting up our first project, Visual Studio 2022. Once it launches, you will get this little window. I am running dark mode, which is why my looks so cool, but you might be running light or blue, which is something you may have been able to select while you were doing the installation and the initial steps. However, whichever theme you're running, the layout is going to look very similar to this. On the left, we have recent projects. You see here that I have collapsed my recent projects, what I have quite a few projects. I just don't want to be struck to with anything. I'll make you feel as though yours is not running as smoothly as well as mine is. But once you start your development activities, visual Studio will kind of archive them to the left to allow you to quickly launch them if you need to. However, We both have the opportunity to get started so we can fill in a repository from an online repo like GitHub or as your DevOps. We can open an existing project or solution. We can open a local folder, and then we can go ahead and create a new project. We can also continue without code. I'm going to go ahead and create a new project. You have different templates and these templates are relative to the workloads that you would've selected during installation. To the left, you have recently used templates. If you add guanine and experimented already, then you would have these kinds of templates listed to your left, whichever one they experimented with. If not, it may be empty decimal problem. The right over is where you have all of the potential templates that you could possibly have based on your workloads. Once again, you can also search and filter. So you see I have a lot here. I don't know where some of them following in the list. I can always type in the one that I'm interested in October, and it will filter this list accordingly. When selecting your template, you have a number of options. You have the language that you want the template to be in. This is a C-sharp poor, so we're going to be focusing on C-sharp B as templates. Then we have all platforms or Android or as zeros. You can filter our according to that. You can also filter according to the project types. So weirdly, in console programming in this particular module, I could easily see a C-Sharp on console, and then it would only produce me the templates that are conducive to these two options. Otherwise, with these filters, of course I can scroll through. If you don't find the template that you're looking for, let's see here. You get this far and you're trying to find C Sharp console and it's not there. That means you probably didn't install the workload. So you can always go to the end of the list and you can install more tools and features which would actually just relaunch the installer that allowed you to select your workloads. You select the missing one, which would be for desktop development. Hello Visual Studio to modify itself. And then the next time you come here, you should be fine. Let us get started with a C Sharp console app. So notice you have C Sharp console up, you also have VB console. Absolutely very careful to note off the language that is being used were not using Vizio OBC. If you'll want to be sure you choose C sharp. Then when I did console, you would've seen two different options, C14 dotnet framework versus the dotnet Core. So we're actually going to be focusing on dotnet Core because.net Framework is older technology. That's when it was Windows only since dotnet Core, not in it has become open source. So we wanted to focus on the more recent advancements with NOT IN IT development and we've using dotnet Core. We'll choose the console app that can run on dotnet Core that can run across all the platforms. Remember, I didn't mention that this is an old cross platform, a slit that just double-click it. And then we will be faced with the menu, sorry, the wizard option to put in our project name, choose a location and select a solution. I'm going to choose for the project name. Very simple. Hello World. That is usually the first program that anybody ever writes in any programming language. Helloworld. Notice that by changing the project name, it's automatically change the solution name, but I don't necessarily want the solution to have the same name as a project. So I'm going to choose this one. I'm going to name this console programming. The relevance of this is that the solution to a project, sorry, a solution to a problem. When you're developing an application, you are developing a solution to a problem. Solution. The solution may have a name, but it has different projects, which is something that we will be doing. So we're going to have one solution that has many projects. So that is why I'm naming them differently even though by default it would have tried to give them the same name. I'm showing you that you don't necessarily have to because there are times when you have a solution and then you have different projects with different names on the same solution. Project name. Helloworld. If you want to change your location, you may do that, but I'm going to leave my default location. And then the solution name is console programming. Then I'm going to hit Next. It is optional to please a solution on the project in the same directory. I'll leave that until we hit Next. Then we have to choose the framework version that we're interested in. So we have dotnet Core two-point one, which it is very clearly telling you is auto support. So my suggestion is don't start there. If you're already doing some development and you have a quart 2.1 obligation out. So just say try to upgrade it as soon as possible. But that is auto support.net Core three-point one that will be in support until I think December 2020 to this dotnet five was like an intermediary between 3.16 and it is going out of support in a bowl me off the same year. But dotnet six houses long-term support and that will be in use until the 2024 or thereabout. It will be in use for a few years. I would suggest you just start with Dutton at six as that has the longest bit of longevity out of all of these versions. That being said, however, with just a few tweaks between each version off the dotnet frameworks, each version of C-sharp has incrementally improved. And most of what you can do in 3.1 is also possible in dotnet six. But then dotnet seeks has also a refined certain processes and the code layouts that are not visible in previous versions. So we're going to do a quick comparison just to make sure that you can appreciate the difference under nuances between the versions. I went to start off with dotnet six. Then we can go ahead and hit Create. That is the end result of Oscar editing our project files. One file really in the Solution Explorer, and a file called program.cs with one line of code or comment on one line of code. I'm going to pause from, From this point we just looked at all we create a project, it's somebody we're going to do a lot more going ahead, going forward. So don't worry if you didn't complete all of the steps to memory. That was a lot of information, but we'd be doing it again for normal, went to pause. And when we come back, we're going to take a tour of visual Studio, this IDE, what it is capable of, and how it will help us with our development pursuits. 4. Visual Studio 2022 Community Edition Tour: All right, In this lesson we're taking a look at Visual Studio 2020 to the user interface, how everything is connected, how it works, so we use it in general. First of all, you'll notice that my Solution Explorer is to the left. Yours by default is probably to the right. You can actually take these what should I say, toolbars and move them all around. If you have a different vision for whole Visual Studio is laid out for you. Personally, I liked is the Solution Explorer to the left. So I actually can just drag it over and docket. You'll notice that these are the squares up here. When you drop it into square, it will show you where it will appear. Should you release your pointing device. If you drop it in the center, then it becomes another tub. I don't necessarily want to be writing code and enough to tab over here to change a file and then come back. I don't like that, so I like to have it to the side and in my case to the left-hand side. And then I don't want it so wide either I can always make it smaller or larger accordingly. Of course, it affects so much real estate you have for your code editor section. You can experiment with that. You'll also see other toolbars on my screen that you may not necessarily have. Any toolbar that you're interested in. You can always go to View and you can see it's if you accidentally close your solution explorer, then you can always go to view and you'll see your Solution Explorer, you click it, it reappears. You can pin it on peanut or hide it. So if I wanted hidden, but then when I hover or click one time it appears and then I use it and then I continue doing what I wanted to do. That's another way to keep it on the screen, so to speak. But have more real estate for writing your code. I'm going to have it docked permanently because of a beginner screen that I can use it, but you may not necessarily have that, which is why I'm showing you how you can alter hide also. I'm just going to focus on the things that are absolutely necessary for us to get through console programming, at least for now as we go along, we will see more and more things. Visual Studio has different themes like I would've mentioned. You'll see here I'm using the dark theme. You can always go to Tools, theme and choose the theme that you like the most or you can get more themes. And when you get to a certain level, you can even design your own themes. So if you started off with a light theme, then your Visual Studio is probably going to look more like this. I don't like that. That is harsh on my eyes. If you chose blue, then I think it just changes the minute items, right? So this is the classic Visual Studio look from Visual Studio 20052008. Is it kinda looks like this or more like 2012 actually. And then you can also, like I said, you can choose other ones. So I've got one off the marketplace called Nordic that kind of has this grayish, bluish hue. I'm just showing you options. Once again, you can always get more themes if you use system sitting, my system is set to dark theme in my windows. So it's just inheriting that from my Windows machine. Once you're comfortable with whole year Visual Studio looks, then you can proceed. In terms of color coding. This is our editor, and it's really just a text editor. If you've ever done any code before, then it's a text editor if you've never written code before and this is your first coding course, that's no problem. That is not a problem. This is just a text editor. Think of it like Notepad. So the only difference though, is that we're going to be writing specific syntax to accomplish specific things. So the color-coding are, you'll notice that certain itself code have different colors and they really signify their role in the whole experience writing code. In the dark theme, at least you'll notice that console has that kind of teal look. I'm colorblind, so forgive me. My clothes are off. But that console has that T-loop. So Console is what we'll call a class that is always going to color code anything that is a class. Then you'll notice right line is white. Functions. This is a function or a method that is going to be white. And methods are usually characterized by open and close parentheses. And then every line, or 90% of the lines that we will write at least and with a semicolon. So that semicolon is very, very important. No, notice if I missed off that semicolon or I misspell something and Visual Studio cannot figure out what I am referring to. It will give you that red squiggly line. And if use Microsoft word, then that is something you are familiar with. This is going to indicate that there is some error with the code that I've written because the syntax as the meat very specific rules in order to be accepted by our editor. Once the editor detects that there's something wrong with the syntax or what we have written. It is going to give us those that are red lines. Sometimes these lines are the arrows. If you hover over the line, it will tell you what the error is. Sometimes it cannot tell you what the error is Alt, rightly right here again, to me that the semicolon is expected, okay? If I put the semicolon, that one goes away. But in this one it doesn't know what we're right. It is it knows right. But it might not be able to determine that lie is just a misspelled version of variety. That is where it may failure. So you can always hover. And then you can click on this light bulb, which will try to give you some suggestions. Here, Visual Studio, especially in 2022, has become so intelligent that it can actually contextually see this time that it is probably just a typo change right? To right. And I knew if I click that, it will meet the courage on for me. And then that line goes away. That this all Visual Studio is actively helping you to write better code. If I made a bigger mistake than that though, something like this. No, I don't know what it can do in this situation to help me because it's just going to say this does not exist, it doesn't know what this is. It's suggesting an error. This one is still seeing. This is a variable that was never used. There is no variable there with that name, etc. I'm just showing you that there are some areas that can help you with and sometimes it's just not going to know what to do. So from time to time, you mean need to end up googling. You know what your error is. Are you just erase everything and tried to write it again from scratch and see whole visa aesthetic and help you. Now another thing that I did not highlight was the fact that we're getting these cold hidden team. By going to the next line, Visual Studio is making an assumption that maybe I wanted to do another line. So by pressing Tab, I can actually accept that grade old block of text. What I intend to do if I wanted to console. But this time, you see I made a mistake console dot. And then you'll see here when you do a dot, you'll actually get this thing called intelligence, suggesting potential methods or properties that you can use to complete what you're doing. All right, So sometimes, I mean, you're not going to memorize every single method to just write. It's their time zone, you just won't. So once you do the dots, Visual Studio is going to make suggestions and see maybe you want buffer width, maybe you want to read line and he started typing and it's going to filter them as it Yes, I want read line. And then you can use that. Another thing to notice on this point is that if you didn't choose that suggestion, something happened, you clicked away. And then the suggestions when till we get the MAC is control and space from the full stop are if you're typing it will suggest it to you. But let's say you press the Escape or you clicked away and you don't even have that autocomplete line available to you. You want to know what your options are. You can actually do control space and then you will see your options. And I'm going to be honest, I've been doing this for years and dear times when I don't know what needs to come next, there are times when I Control Space and I scroll through onto something looks like what I'm looking for. And I'm sure a lot of experience C-sharp developers will tell you the same thing. So I'm just saying that to say there's no shame in getting this far and not necessarily being sure, what do you want to do next. That's why Visual Studio is designed this way to give you that IntelliSense to assist you so you can be scrolling. And then he said, I really want to write something or I wanted to take inputs. I want to read something, AAC read, read, read, read light. Maybe let's try read line. And then he can use your tab and an autocomplete that, right? I mean, I'm not able to show you every single nuance and everything about Visual Studio in 15 minute video. There are things that you would just speak up as equal along. And as we write code together, I will be pointing certain things old. I will always show your keyboard shortcuts. So, you know, like writing a comment in C-Sharp would be slash, slash or slash asterisk and an asterisk slash. And this one is, allows you to do multiple lines of comments. All right, so if you need a threat to a paragraph, you would use this one. If you wanted just one line of comments, you'd use that one. Because the next line wouldn't be commented. Keyboard Sharp code for it. That would be Control key and see if you have line of code that you no longer are. You don't want it to execute. You want to come in to told you hold on, uncontrol, you press key and then you press C while still holding down on control. If you want to uncomment it, it will be Control key. You, you're holding down Control and impressive letters K and C to comment, and then to uncomment. Holding down Control. You press key and you, those are little things that I'm going to be showing you if you want to duplicate this and you do Control and D. All right, our control CV, which is really a copy and paste, but you notice I didn't highlight the line and say Copy then piece I just had the cursor there and then holding down Control C and then v, and then it just duplicated it. Control D may work for you based on your development settings. It mean not to have had burst and see those not work for them, but control CV generally works in that way. For the final bit of the store, I'm going to show you how you execute your application. So at this point we have some code that is supposed to print to console or where doing console programming. Console programming because at the most basic level, in most languages that are designed for desktop, you're going to have a console. So when we say console, we mean like command line. If you've ever done come on line on your machine, what it's Windows, Linux or Mac. It would look something like this. This is your console. So when we say console dot write and I, and we're actually calling the underlying functionality that uses this command prompt window. And seeing that I wanted to print whatever text I have outlined here. This window. When you're going to be testing your application in Visual Studio, you have the option to either run it, and this is using debugging. Run it without debugging the keyboard sharp bullets would be F5 to mimic debugging and control, plus F5 to mimic no debugging. Later on, we'll look at what debugging means. The general net effect is that when you press these either one of these play buttons, it should execute the code that you have written. And it should pop up on screen and showing you what the alt come off your code is, whether or not it's desirable now is where you programming comes in, you make your modifications and you can get it to the point you want it to be. But to run it, you're just going to press the Start button. And then it starts debugging CDC, the output window is coming up and is give me all sorts of stats. And then you get that console window that looks just like a command prompt. And then you get your line HelloWorld. And he's telling you that the code executed from this location. That's an executable file. All right, so any installer, any application you run is usually an executable file. And then it says it will automatically, well, they're giving you the option to automatically close it, but we don't necessarily want that. We can just press any key to close this window. So if I press enter, it will just close the window and return us to Visual Studio. And that's really it. So that was a very simple Hello World application given to us by Visual Studio. So yes, the project was called Hello World. But the code was generated for us not because the project was called that. Before I leave though, let me give you a little tour of the Solution Explorer, even though I'm going to expand on this a bit more, here is the name of the solution. So remember I said that we had a solution different from projects or projects. So we have the solution called console programming. And then we have the first project called helloworld, which one-click will reveal an XML file that allows us to change certain things. We're not getting into that right now. Then we have dependencies. You don't have to worry about that, right? No. And then we have one file called program.cs, which is our class file hosing over cold. We cannot multiple files, of course, in our project, which we will be looking at as we go along. So that's really it for the tour, the general tour of visual Studio, what it brings to the table and will help you to write clean and wonderfully executable code. When we come back, we're going to look at the difference between a dotnet six project and the previous versions of dotnet. 5. Understand the Difference between .NET 6 and Previous Versions: Alright guys, so wonder we were here the last time we created our first console programming project, we call it helloworld. And we explored some code. We also explored Visual Studio on a whole. And what I wanted to do is just explore the difference between this console programming template and the ones that we would have gotten from dotnet five or 3.1 or even dotnet framework if we were to use it. Simple, simple way to get a new project is directly core solution. Alright, so remember Solution Explorer. We have the solution up top and it's characterized bed at purple ribbon inside that window. And then the project has the badge that gives us the language that this project was written eaten or is supposed to be written in. So we can right-click the solution. Then we go to Add. Then we say new project. Then this screen should look very familiar to you. This is the same screen that we use to add the first project. We can choose console up. And because I have on my filters, I'm seeing it up close and personal, but if I just clear, then I will get bumped medalist, I'm going to go with a console app. Then this one I'm going to call it hello world. No one suggestion when naming your projects. Don't use spaces. I suggest that you don't use spaces. That's one. All right. Don't use spaces in the name of the project and camelCase your words. You'd notice that my Hello has capital H and the world as capital W. For readability purposes, it's one word, yes, but at least with the capital letters, you can see where one word stops and another one starts in the contiguous block off characters. I would also suggest that you stay away from special characters. That actually is the only one I really use is an underscore in naming projects. And these are more suggestions because later on you can end up with some issues that other platforms don't like, dashes and stuff. You can use an underscore and sometimes you'll see people use a dot. Not just perfectly fine off course. So I can say helloworld dot and I'll call this net five, that we know that this is the Hello World application and its relative to dotnet files. So that's why I named me is very important. There's no indication that this one is done at six really. But because the whole course is built our own dotnet seeks not going to be specific about all the projects being done at six. I'm only highlighting this one because this is the outlier. Helloworld.net five. And then we click Next. And then this one, I'm going to make sure it knows that I'm using dotnet F5. Then I'm going to hit Create. Alright, so now our new project is, and if you look at it, you'll see that we have two projects. If I collapse them, you'll see them individually. You'll see the HelloWorld and you'll see helloworld.net F5. If I explained Hello World, you see the HelloWorld files. If I expand HelloWorld, done it five, you see the five files. Notice that the tool projects at least at the base of our identical in terms of what you get. You get the program.cs file. Let us compare these program.cs files. We already established that this is what the dotnet six program.cs file looks like. Nice, clean, literally one line, we added that additional land. Well, let me go back to the defaults. That's what we got to hold off the box. Now look at the dotnet F5 file. There's a lot more going on here. Well, what do you call a using statement? So I using statement is a statement that says I need to use this library on your system. So every Windows machine, every Markov or Linux machine, they have certain libraries, are certain compiled bits of code that are available at the system level. That when you're writing an application, you can actually write an application to access them on any machine. When we say using system, it means that any machine that it's going to be running on, please try and access that library calls. This system library is what is important for our console up to run, which is why I said it uses the command prompt. When we include that, then we have access to certain functions, are certain bits of code that lowest access by itself, the system. You'll see this one called namespace. No, namespace is the code representation of the folder that the file is located in. So simply put, every project that appears on the disk, Project Explorer is really a folder in our file system. All right, literally it's a folder. So if I right-click this and I see open, sorry I missed there. If I right-click and I say open folder in File Explorer, it will literally launch a file explorer showing that sense of files, all the files involved in the program. If I go up, That's console programming. Console programming, that is one, that is the name of the solution, That's one folder. Then you have that folder, okay, nothing is in there. We also have hello world. Remember we. Screw it to that project. In the previous lesson, we have hello world, dotnet F5. That's another project. I'm just showing you that. That's all the namespace really is. It's just the name of the folder. So if you have subfolders and input files in those sub-folders and the namespace would automatically be fuller dot, dot, dot, dot for the whole hierarchy of folders window. Next up, you'll notice that it has class declaration called internal class program. And it says open and close curly braces. And we have a static void main function, which then it goes down to print our helloworld line of code. So the only real thing that these two have in common is that they're both using console dot read line to print. Know what the engineers at Microsoft did for dotnet six was reduced a lot of the repetition because in all the versions of.net Framework up onto the net five, this is what the code would look like. At the very least, by default, it's always starts off with that glass and it always starts off with that mean function. What they did was the Echo Dot repetition. So everybody knows that these two are required at the very minimum. So they said, Well, let's just make it implied. We don't want that console needs to use system so we can meet that's implied also. And we just get straight to the coding non-points in the soul because based on the version that you are able to use goes down and it's six is limited to Visual Studio 2022. Well, if you're using twin to 19 for whatever reason, and you have to use done it five instead of done it six, then this is what your code will look like. But everything that we're going to be doing for dotnet seeks, it is very possible for a dominant fire. Just remembered that all of your code is being written inside off the mean function and everything operates her own main function. If you have to go to another function, then you do that inside of the class. If you'd have to go to another class, you have to do it inside the namespace. I don't want to confuse you guys. I just wanted to show you what the older C-sharp templates look like versus the newer C-sharp templates and help you to appreciate why one looks the way it does and why the other looks another way? No, earlier we had clicked to, with one click on the project, were able to see this XML file. Here it's that the unit at the output type is dot EXE. That target framework is dotnet six and implicit new usings are enabled. We'll look at that later on, and it is enabling no level. We'll also look at that later on. If you look at the dotnet five, you'll see that it has fewer configuration parameters, but it is just saying that the target framework is 5. Still the same output tag. If you do dotnet Core three-point one project, it would look just like this project template, code template, except I think this would probably be public instead of internal. We look at the difference between those later on and the XML file, the project configuration file would look slightly different also. However, like I said, we will be focusing on dotnet six. So I went to leave the dotnet five project there for reference. But we will be focusing on dotnet six going forward. 6. Development Using Visual Studio Code: Hey guys, In this lesson we're going to be looking at an alternative to Visual Studio 2022. So you may need an alternative for a number of reasons, Visual Studio is really created for Windows and Mac OS machines. And your machine in general just might not be doing a good job off running Visual Studio, which is okay because it is a very huge application that requires certain resources that not every machine can regularly provide. That's fine. So Microsoft has given us a nice lightweight alternative that is cross-platform, meaning it runs on every single operating system and it is very easy to set up and use, and this is Visual Studio Code. Know the first thing, there are two things that you need. One Visual Studio Code, but you also need to manually install the dotnet six runtime. So you can get to that by doing a simple Google search.net six Runtime or ASP.net Core six ruined time, whichever one, then that will allow you to install the SDK on any one of the operating systems that you have. Once you do this, it will install the binaries in your system and you'll be able to use dotnet six. Now if you have Visual Studio installed already, it came packaged with it. So you don't necessarily have to do this step again. Alright? Once you have the runtime, of course, you go ahead and download Visual Studio Code. You go ahead and install whichever one is suitable for your operating system. No-one's Visual Studio Code is installed. You'll get a simple enough window that you can increase or decrease display off by using Control Plus or Control minus on your keyboard. No, from here, you'd want to set up your project space. What I like to do is create a new folder and then use that folder, my operation spot, so to speak. So I went to open folder. And by opening folder it will ask me which folder I want open, navigate to where I store projects. Then in this projects folder, I'm going to create a new folder. I'm going to call the console programming just to stay in line with all that we've discussed before. Console programming, and then select that folder. Once I have this folder, I'm going to want to save it as a workspace also. So I can just see a file and Save Workspace As. And then I'll just leave this as maybe console, console programming workspace. That I know that once I open that file, it will open up this folder with all the projects and everything in there. I can see if that outside of having the workspace, I would want to have folders per project, just the same way that Visual Studio, each with each project that we created, give us a new folder and then you wait to IRange the related files to a certain project. I'm going to create a new folder instead of this workspace. And I'm going to call it, let's say helloworld dot VS Code. Spelled incorrectly. I can always right-click and rename. There we go. Hello world. Yes, quote, know, to create the project in there, unlike Visual Studio, gives us a nice wizard and a visual user interface. I have to use commands. I can go to determiner, bringing up a new terminal. And then inside of this terminal after make sure that I am pointing to one, the card folder and then to run certain commands. So the change folder, what you want to do is say cd and then start typing the name of the folder you want. So I want hello, world, I can press Tab and it will autocomplete that for me. Press Enter. No, I am looking at the folder helloworld. That path. No much is the folder that I'm targeting. Mixed. I want to actually create the project. So I can say dotnet just by writing.net, you can see if you have the runtime or the SDK installed properly. If you don't get something looking like this, then you probably need to go and try and install it again. But I can say dotnet, new console. So I'm seeing dotnet, the cape. Please give me a new console project. And just by pressing Enter is going to fill out this folder that I targeted with files that are conducive to doing console programming. When I click program.cs, which is a C-Sharp file, I get my one-liner, just like all we saw, that program.cs in Visual Studio. You may also get a pop-up saying that you need additional assets. You can say yes. Now another thing that is very important for your experience here in Visual Studio Code, extensions for Caesar programming, you may have gotten a pop-up saying. They suggest that extension if you didn't get to, that's fine. If you go to Extensions, then you search for a C sharp. You will see at the top, C-sharp for Visual Studio Code poured by Omni Sharp. Okay, that's nice to know. But the relevant part is that you want to definitely install this so they get some code hinting on some intelligence to help you with your C-Sharp programming in diverse in this interface. So you would see on Install button like this when you click on that extension. So you can go ahead and install it. And once you have it installed, you can proceed. Now to execute your application, what you'd want to see is dotnet run. Say dotnet run. It was start compiling and then it will show you the output or the results instead of the terminals. So the cool thing about determinant is giving you direct access to the same kind of console that would pop up every time we run an application in Visual Studio without going externally in launching a whole other console, you can do everything right here in this interface. You can execute, you can go and run. You can start to debugging if you wish, which would give you a slightly different experience if you start at the debugging. But the point is that you would actually see everything inside of Visual Studio code without actually needing to launch an external window. Of course, every detail has its pros and cons. This one is nice and lightweight and you can see that it's brings us slightly different flavor to the whole development experience. But that being said, everything that we're going to be doing in Visual Studio is actually repartee, replicatable, replicable, whatever that word would be. But it can be mimicked in Visual Studio Code to help you to have a very similar experience. The last thing I'm going to show you guys is how you can manage multiple projects inside of this workspace. So let us think of our console programming workspace as our solution. And then we have different folders that represent each project. Inside of this console programming folder, I would want to create a new project. Let's call this one hello world, just like what we did in Visual Studio. Hello world, dotnet f5. Let me get my spelling right. There we go. Then if I wanted to create a project instead of this folder, I have to make sure I'm pointing to that folder. So I have to say something like CB. And then I went to see a dot slash, dot slash sawed off the Goldbach. Because look at it. The path is HelloWorld VS Code to see cd dot dot to go back into console programming. So the NCI CD and then start typing Hello World and press Tab until I see the folder that I'm interested in, which is.net five, press Enter. And then I can say dotnet new console. And just by using the up and down arrow keys, I can go through recently or previously typed commands. So I have to say dotnet new, let me increase the system, makes sure that you are seeing clearly dotnet new console. But when I went to specify the version, I have to say dash F net F5. So this would only work if you have the dotnet F5 SDK already installed, which you probably do if you install Visual Studio. If you install the SDK, manually the nail after, go back and get that particular version. But when I press Enter, notice inside of the donut five, I'm getting that new project as well as the project templates, the code template for HelloWorld and done at five. That is essentially whole Visual Studio code would work. What you can do is for each budget that we will be creating in Visual Studio, just create a new folder, run that command, and then you can start coding accordingly. 7. Section Review: All right guys, we've come to the end of setting up our development environment. At the very least, four are in diverse a hit, so forth, C-sharp console programming. We have two tools at our disposal. We have Visual Studio 2022. We're using the Community Edition, and we see here that it is a verbal full tool that Microsoft has invested a lot in to make sure that as dotnet developers, we have a fair, comfortable workspace to use. And it is going to help us to write some clean and Paul full code. We looked at how we can rearrange it for your own comfort by moving these Toolbar sections, the different parts, looking at the different themes whole weekend, it executes a program. We can add multiple projects to a single solution and everything like that. Outside of that, we also looked at using Visual Studio Code. Visual Studio is not an option for you whether it's because of your OS or your system specifications. Visual Studio Code is a very, very lightweight, capable, and perfect alternative to using Visual Studio. There are other editors out there, but those generally cost money. So I'm just showing you all of your best options without having to spend much or if any money upfront. Visual Studio Code is a nice lightweight editor that allows us to, it gets our projects created with a few simple commands in a built-in terminal and get to writing some code with all of that, sit and don't stick around. We're going to start focusing more on the C-sharp language as we go forward. And we will be learning how to build some beautiful applications. 8. Understand Basic C# Syntax: All right guys, so in this lesson we're going to take a step back and look at how we can continue our development in diverse by launching an existing project and the proceeding with programming? No, I hadn't mentioned from when we're doing the setup that to the left you'll see recent projects. So here are a bunch of my recent projects. But here is the one that I wanted to focus on, which is the one that we have created together. If you shut down your Visual Studio, shut down your machine, you went to have dinner, whatever it is, familiar buck, you want to jump back into a project that you're working on or a solution you're working on, then you would see it on the left. Most recent projects know there might be a time where you work on so many that you don't see listed there, you can always go to open a local folder or open a project or solution rather. So you'd want to open our project or solution. So let us state that route because this one, it says easy as clicking it and it will bring up Visual Studio with the solution. If it's not there, then you want to go to open a project or solution, which will then allow you to burrows to where the project might be. So you can actually just browse through until you see the project or the solution folder name. And then you will see this file here, which is a solution file. I'm Solution files. Any FCS approach for us, we don't see in the CS project file from Visual Studio Code. It's a CFI that one we click it in Visual Studio brought up that XML configuration. The solution file would launch Visual Studio with all of the projects and files associated with the solution. Generally speaking, the name of that file will be the same name. They would see as the folder name. If you double-click that, it will actually do the same thing and launch Visual Studio with that solution. Now that seems solution file can be found from your file system if you were to navigate there and you can, I can easily navigate by right-click and say Open File, Open Folder. So if I was to navigate here manually, here's that file. If I double-click that file, it launches Visual Studio with my projects. I'm just showing you how easy it is to resume where you would have lift off. Knowing this part of the lessons we're going to be focusing on C-sharp language, the grammar, vocabulary, and general beats off syntax that you would use to write code. We're not going to learn the entire language here and I'm not going to be div, being too deeply into certain things. I'm just giving you a broad overview of what C-sharp looks like. C-sharp is the premier programming language given to us by Microsoft for the.net platform. It has a close resemblance with C plus plus RC language. So it's a part of the C language is kind of botch. It also takes a lot of its constructs from other object oriented programming languages like Java. If you're alert, if you've learned C, and if you've learned Java, than a lot of what C-sharp is doing will seem familiar if you've learned neither. And this is your first time doing programming. Once again, no problem. I'm going from the very basics, so you'll be able to catch on. Now C-Sharp on this point is at version ten, he does gone through many versions with each iteration of the.net framework into dotnet Core. And I can just delete, keeps on getting better and better. But one thing that I must come in Microsoft with is their ability to update the language while keeping certain older regimes, arrangements or paradigms alive. So even though it may introduce a new way to do something there, all the way off writing it in older versions of C Sharp won't get deprecated. It's not like it's going to say, oh, that can't work anymore, you have to change it. So they do an excellent job of upgrading. Destroying older code. C sharp is also open source and you can go to their project repository on GitHub by going to github.com slash.net slash C-sharp lungs. Open source means that everything that you are doing the have made it available. All of the underlying code that they have written represent our owned that you will be using. They give you the shoe, the implementations and everything you can go in and you see exactly how it works. You can even make contributions here. You see here that it does 125 contributors. Sure, not all of those are direct Microsoft employees. So as you get more and more comfortable, we can start looking at this library, looking at how certain things are done and seeing if you can improve them. Also. Know earlier we were looking at certain things that are illegal. There are certain things that you just cannot do in the syntax. There are certain Tolkien's that server specific purposes. So like a hashtag or a number sign or pound sign has the very specific rule of opening one-off these I kind of just say pond. I can say Poland error. Sure. When I can say something that I version, notice that I'm getting this red line on the version. It does because it is not something that is in the vocabulary. So just like with English or any other language that you would speak, there are certain words that are just not in the vocabulary. Words that you don't use because they're not apart of the language, is the same way when we are writing C Sharp or any other programming language for that matter. If the language does not detect what you are writing as part of its syntax, then you will get that kind of red line. Let's us start off with what a comment. A comment is a good way to document what is happening in your cold read. So we can write a comment by using slash slash. And then we can see this line prints hello world. So this is a good way of informing what won, reminding yourself what the code does or to informing somebody else what it's supposed to do. If you have a whole paragraph that you want to write. So you can see slash and asterisk. Notice that everything after the slash and asterisk became green. So that's just the color coding to show you that it's a comment. But then you can close it with another asterisk and another slash. I didn't want you to do that. Anything that you read in-between the asterisks would be seen as a comment. This is a whole park off comment in multiple lines. So this is how you can write like a whole paragraph describing what is happening in a whole block of code. So this is for one line at a time, this supports multiple lines. We also have what you call a statements. A statement would be an expression that ends with a semicolon. So in English or most other languages, statement is usually the sentence also on comprises of words that usually has a specific order or grumbles. So in English you would say the adjective before the known. In Spanish, you see the known then the adjective. But the fact is that That's hold. A statement is written in that particular language. In C-Sharp, this is whole statement is written and you should always end with a semicolon, even though in another language you'd end with a full stop. If you have a statement declaring a variable, for example, and I'll explain what a variable is. Well, let's say var name is equal to variable is a temporary storage space for detail. And then I can see my name. Is this. That's a statement that red line is saying, Well, you need to end your statement appropriately, so I need a semicolon. So one way to know when you need a semicolon is that if you write the statement and you see that red line, chances are you need a semicolon at the end of it if everything else looks okay, but you still get the red line. Check and see if you need a semicolon. Now there's another construct called a block. A block would be similar to what we saw in the C-sharp five template, and it is denoted by open and close curly braces. So these are blocks. A block would be like a paragraph in our written human language. Blocks can be namespace, it can be for our class. You can also be for method. I didn't mean it as you go in, you get blocks for if statements and repetition statements outside of the ones they examples here with Aeneas's, the class and the method. If I was to do like an if statement, I would say if name. Don't worry about this. I'm going to go through all of this. I'm just showing syntax once again. So here's a comparison. If name is equivalent to. And then here it's showing me that I'm missing something. So this is one of those times it may suggest a semicolon, but this is not a statement. A semicolon is not what is missing. So I need to write the cart syntax. There are times when you may say, why do I have to do it like that. I generally say don't ask why if the language says this is how you do it, just do it that way. Sometimes when we get fixated on the why it blocks all the fact that that's just the way it is. I'm going to say if name is equal to something, obviously this is not true. But I'm going to just started up a new block. This is saying if this is true, then I want to execute this block of code that is denoted once again by our curly braces. No. Do you remember that we have to import what we call namespaces. So I may have said libraries, but this is a library, it's a namespace. A namespace is really a collection of classes. C, namespace has one class equal to multiple classes. That is a namespace and the ones who compile that namespace, it becomes multi color libraries. The different libraries of different classes that you're taking advantage of. Soul console is a class that is found in the system namespace or library. No one, C-sharp six, you can always add, you're using steam and soap top using system. You can always do that. And as you go along, you may need to know it's grayed out because it's already implied it's unnecessary. But I have System.out and then you have different things here. So you could say System.out detail, you could see this and that whatever. The fact is that if you're not actively using our class are coded reference phoned in the namespace. Then Visual Studio kind of gray told actually that it's not relevant. Now there are times when you have certain namespaces that you want to use across multiple files. Now in the older versions of C-sharp, you'd have to actually repeat that every single time. So for every class that I'm going to use in console in, I would have to have that using system, using system, using a system. In C-Sharp six, we are afforded the opportunity to add what we call a global usings file. So I can actually just create a new file. And I went to call it global usings. So right-click on the project. Notice multiple projects, but I wanted to inside of our C-sharp seeks HelloWorld project. Right-click that project, go to Add. And then I can say new item. And then new item allows me to add a new class file or other types of files. So this time I'm focusing on our new C-Sharp class file. I'm calling it global using this dot cs, and then I can add it. And then from here, I don't need all of these are I don't need all of that stuff. I can clean it off that. But no, I can add all the using statements that I know will be globally used throughout my application to make it. So I will just say global in front of it. So just say global using global, using global using no, I don't have to manually add these using statements in 51015 files. I just have one please. And then I can just keep my code file clean and dedicated to my code. Now, let's bring him back a little closer to home and look at some of the best practices when we were just writing our code. One thing is indentation. When we have blocks of code, we want to make sure we're doing indentation because you don't want to be having everything on one line and then you don't know where one curly brace opens and closes, right? So it will be always good. Anytime we have a block of code, make sure you indent. Another thing is that applications in every programming language goal by three control structures. We have sequence. Then we have decisions not necessarily in that particular order, but we have sequence, we have decisions. And then we have repetition. Sequence refers to the fact that it will always go in the order that you've written the code. Just know you saw me take these two lines of code and put them inside each Stevens and then we got an error. Why? Because I am checking for a variable called name, which does not yet exist. The only way I can write an if statement against this is if I already made it exist. So that's the sequence I have to make sure it exists, then I can do processes against it. Alright, so that's a sequence. It will always run from the first line. So the last line in that exact order is good when you're working on your algorithm or the flow of your application, the logic that you will see, I need this to happen then that, then that, then that. And then you write the code in that exact order. Step one, step two, step three, etcetera. No decision is also called a conditional statement. It means that I'm going to take this action should this condition be true? So if this condition holds true and we'll be looking at the different conditions and how we can write them. But if this condition is true, then I wanted to get this auction. Whatever code is inside of this block would be like the thin. Because if we were seeing that in English, we would say if it is cloudy, then I wanted to do with this action. Then he would say something like else, do another action. That's all we think as human beings. And that is exactly a whole. We have to write our applications. So after say, if that holds true, then inside of that code block, I defend what I'm going to do. And then I can see else, do something else. We'll be looking at that later. And I'm just once again giving you an idea of what we mean by decision or conditional statements. The next one would be repetition. So if you have something to do multiple times that maybe print hello world 50 times, you do have the option to just write that 50 times, which of course is not very sustainable. Or you can do a repetition. So you could do something like loop. And I'll just do a quick for-loop here to explain the syntax. Yet, I'm just showing you what you would say for some number of iterations. All of these just define only to see a whole many times you want it to happen. Do this action once again, you can see it's in a block. The reuptake, the inside of that block would be repeated for whatever number of times you've defined here. Alright? So those are some key components to writing programs in general. But then C-sharp syntax, of course, it makes it very specific. Wholly go through using Visual Studio. I'm not going to get too much into all of the syntax. What I will do is leave some comments just so we can remember what was discussed here. And I'm just going to erase anything that is not completely important to this Hello World application. And I'm just going to say there are three control structures in C-Sharp programming. Sequence. And I think sequence is the most important. So if there was an order of precedence sequence called his first decisions and repetition, those are more based on your need. Input sequence definitely governs everything because it always goes into artery that you've written the code. That's really it for just a broad understanding, broad look at C Sharp syntax. When we come back, we're going to create a new project. We're going to look at how we can write an actual program that interacts with the user. 9. Input and Output Programs: All right guys, So we've been learning C-sharp. We've been getting familiar with Visual Studio. Let's write a real program, shall we? So I'm going to create a new project for this new program, I'm going to right-click or solution, go to Add New Project. And then we want another C Sharp console application project. I'm going to call this one input, output. Input output Clinton. Next, we know that we need to work with dotnet six and then we create. Now of course, if you are using Visual Studio Code, that means you'd create a new folder, do a new dotnet console program, and then you will be at the same stage as we are, so forth. This application on what we're going to do is I will just write comments. One, declare what we call a variable. We're going to low user input and store in a variable. Then we're going to print contents of a variable or the user's inputs. Alright? So it doesn't visualize it anytime you're using an application, whether it's whiteboard desktop, you usually, as the user would put in detail, press, Save or something. And then later point, you'd need to see represented to you by the program or saved onto milliliter point. We're not quite at the part where we're going to see if it's until tomorrow. But for null, we can at least see how it is that we receive input from the user and then send it back. So typically, computers do three things. They accept input, the dual process, and then the produce an output. Those are the three processes of any computer. Tick inputs, process it, and then send back output process, of course, could be as complicated as a math equation on, it could be something else. But whatever we do inbetween, taking the input and producing an opiate is called a process. Alright, let us look at declaring a variable. Now C-Sharp has different datatypes. A datatype is pretty much like an adjective that describes the variable and it defines or tells the variable what kind of data it can store. Data types in. C Sharp can be. Let me just this data types can be and are not necessarily limited to. I'm just showing the basic ones. That will be string. That would be like words and numbers, like a license plates, like a name or a license split number. As I said, Names and Numbers. Anything that wants it contains letters. It can contain numbers, it can contain special characters. Well, that's what we call it a stream. We also have numerical data types like integer, which would be more like whole numbers, which would be more like decimals, then you actually have double slash float. Did more recent C-sharp versions, you actually have decimal as a datatype, but I'll just stick to the traditional ones just in case where on different versions they have integers, you have double float. You also have like char. Char represents one chiropractor. Alright, so it could be a letter. It could be, I mean, this is just one. So that's the example of it. The letter E or the number seven. It's just one thing at a time. It could be a special character. Those are all examples of chars. All right, let me get my spelling rights. Strings would be my blocks off, takes those blocks of texts, we'll use the double quotation mark. Notice the char uses a single quotation mark. In an earlier example, you would have seen me use my name. And in the default example you would see Hello World, that is a string. All right? You have different datatypes and we'll be going through others. I'm just trying not to give you an information overload, but these are typical examples of different datatypes. So like I said, it's like an adjective describing what the variable can store. The variable is the actual storage point. So to declare a variable after the datatype, then I give it a name. So if I'm going to want the user to enter their name, then I would call the variable name. So the thing is that you want to always be as descriptive with your variable name as possible. You don't want to say string aches. What is x? Alright, when you have to describe to somebody who is looking at your code or even try to remember what x was used for. Two weeks later, you will not remember when you see something like name. It is clear if you want the edge, you would probably want to use integer and C, H. That is clear. If it is something that is more than, more than one word like maybe full name, you'd want to see something like full name. No notice how I wrote this one. There are no species. Species are illegal in variable names. You can use special characters as far as an underscore, that's the only special cartilage that is allowed. You cannot use a hyphen, you cannot use anything else with an underscore, will do that way. Some people like to use underscores personally, I don't I don't like to use them. They are illegal. They're nothing wrong with them. So if you want to use them, no problem. I however, rely on what we'll call camel casing, which is when you make the first letter come on and then you capitalize every other words. You see here is an example of Kamil in case like when we named our projects, we would have used pasco case. If I said Hello World as a variable and I can fertilize the H and the w, then this will be Pascal casing. Alright, so we capitalize the first letter as well as every ADL. First, that's off every word in there. Generally speaking, when you name your variables, you want to use camel casing because it improves readability and anybody who looks at it, you can tell that this is a variable designed to store the full name of whatever. All right, so that's why naming is very, very important. So that is our verse simple variable. All right? No, That was number one, declare a variable. We looked at a different datatype options based on the information that we want to get. String is the best datatype for that information. Right? Now we need to allow them to input that variable. So, so far we know how to output, because console dot write line is what allows us to output. However we need to input. So where do onto right, we want tool. If you said read the near underwrite truck, we want console dot read, line. See you that I always say console.log deadline. The console will actually pause and wait for inputs because it's not reading something. As opposed to write land where it's going to print out something. Alright? No ofcourse when we allow the user to insert whatever the read line we need to store it somewhere. Because when they press Enter after the type within emperors enter, the inflammation is sent back to the program. But whereas the information going, that is why we have the variable. The variable here with the green line is complaining that it is declared, but never, you never used because we're not using it to do anything. We just have it there. So the presence of it is important. Sure. But it's not doing anything. So we wanted to see when you receive input from the console, please store it inside of this variable. Went to see a full name. You will get your value from whatever comes in through the console. All right, so there are number of ways to write this code. All right, I'm just trying to show you the simplest way you can get on your feet and start working. One makes sure the variable exists to assign the value to the variable. This is called an assignment where whatever is under right goes into whatever is on the left. So an example of an assignment, we did an example earlier, I could see a string full name. I'm assigning you the default value of maybe an empty string, or you should have the default value of my name. All I'm doing is seeing create a variable and assign this value to set variable. If I do not put the assignment, then the variable will exist with nothing in it. So it's what we're going to call null, which is just like a receiver. There was nothing inside there until we do an assignment like this. All right, after we assign the value that the user enters into our full name, then I can print console, dot, write line. Then Visual Studio figures that I would like to print what is in full name. So you've seen console dot write and then lots of wonderful weekend print a literal value like we did Hello World. In this case, I don't want to print the static string because the user didn't enter helloworld. I don't know what the user entered, whatever to enter the stored in full name. That is what I wanted to print. So instead of writing out all these quotation marks and those. That block off string. I'm going to just print the contents of my string variable back to the console. At the end of this application, once again, we are creating a space in memory. A verbally is basically a space in memory, a storage space in memory for the time application is running. As soon as the application stops running, that variable no longer exists when you start to top it creates it. Then it waits what input? Then it does science and input to set variable, and then we print it. So let us state that for a spin. Know, you'll notice that the play button up top students is Hello World. That means if we press bleeds still going to run the program.cs in HelloWorld, we don't want it to run Hello World. We wanted to run our input output program. We can actually change this by changing this drop-down list and choosing the program that we want or to project that we want to run, which would be input-output. You'll also notice that when you change the one, the project that is being focused on at that point, he's the one that gets the bold letters in the name, right? So if I change it back to Hello World, hello World is bold. If I changed the input output, input, output is both. All the way to do that is directly the project itself. And click Set as startup project. That does the same thing that a drop-down list up top here. If I want input output, right-click Set a startup project. And it will not focus on input output and the Play button will show the same thing. When I press the Play button, notice that the console is on the screen and it's just blinking. Okay. Why is it just blinking? It's not printing anything is not proceeding wanted created or variable shore, but it's also waiting on input. Output, my name. Then press enter. It will proceed to print to the console and then you notice it stopped. God, that's all I told it to do. Weird for you input print and linear done. This second line is what it is printing. This is what I entered. Now this is not very intuitive. I'm sure you're seeing that it's not very intuitive because you just paused for input. I wrote their applications. I know what the input is that it is pausing on waiting for you. If you were to pick up this application for yourself without my guidance, would you actually know that this is what it wanted? You wouldn't, and that wouldn't expect any user really know that saw what you would want to do for this kind of application. Just like any other application, if you're spending a lot of form, they usually tell you what they want in the text box or for that particular input so that the user know what you're doing. So you always want your user to know what they need to do. You can always print, holds your own messages to screen. So here I went to say console dot write line. I went to give you the instruction, enter your full name. And I'll just put a little colon under, of course, this is what is being printed. So this is a literal string being printed to the screen and say you wanted to look nice and presentable, Nice itself instructions. And then it will pause for input. Then what is being printed. I don't know what's being printed. So I could say something like console dot write line. Your full name is, and then we print to the screen whatever the user entered. All right, so these are the things that enhance the way your obligation. You do have. Console dot write. First was console dot write. Console dot write is going to print it in one line, whereas console dot write line is going to move it to the next line automatically. Let us try this one. So go ahead and run. You see here nowhere seeing enter your full name. And because we did a write line, it automatically went to the next line to wait for input. I went to see my name. Then when I press enter, your full name is printed it in one line because I said right. So if I wanted a prompt in one line, I would just say right instead of one, right? And we'll write line automatically brings to the next slide. And that's pretty much it. Do you see? It's not that hard at all. Once again, sequence matters. Create the variable, print and ask the personal for input, then weighed four inputs, and then you can print out whatever afterwards. All right, so that's a simple input output. No one quick refactor that I would like to show you to this is that when you are asking for data to go into the variable, it is perfectly fine to actually just define the variable and assign it at the same time. Of course, you can't have two verbal assignments on the screen. If you, if you create a variable before you do this a second time. But here what I'm seeing is creates a variable called full name and give it whatever comes in from the user. So that's actually fewer lines of code. So sometimes it's worth creating a program that uses fewer lines of code. Sometimes they'll readability, you want it as explicit. So I'm going to leave it like that for, for your consumption. Create the variable, allow the user to enter storage into variable and then print the contents of the inputs. 10. C# Data Types and Conversion: All right guys, so in our last application, we took a quick look at how we can declare variables. We took a brief overview of the different datatypes that these variables can have. And then we looked to accept and print out information from the user. Now we're going to build on both of these concepts as we looked at variables and their data types. Once again, if you close Visual Studio and you need to relaunch it, you can always just open, sorry if you close Visual Studio, I need to relaunch the project. You can always just relaunch Visual Studio 2022. You can look for the recent obligation or project that you've been working on or go to open a project or solution. Browse to where you would offset the project location to be. Find it, then launch that solution file. You can also do this step from your Explorer itself. So let us proceed. We're going to create a new project. So I'm just clicking on the solution, go into new project, console up. And then this one is going to be variables and data types bearing in mind or very strict naming, suggestions, null spaces and special characters and Pascal casing. So we do all of that. Next we're using dotnet six and then we can create know in our brand new program.cs file. I want us to look at the different variables that we can use. And we're using practical examples, someone to be seeing variable declarations and types. In this application, we're going to create an actual kind of form data input form for our user. We want name, age, maybe salary. There are gender and if they're working or not. All right, let's do all of those. And in doing so, we'll explore hall. We convert datatypes between what is input on what is needed based on the data type that we selected for the variable and how we can print everything all today, end of it. We already did an example with the full name. So here I can see a string full name is equal to. You generally want to stay away from, from Knowles. Null, meaning that I just say string full name. There's a variable called full name, leave it be, it is generally wanted to stay away from that. It will work. But when you build a bigger applications, you want to stay away from that. So you generally want to give it a default value. So here is a built-in default called string dot empty. Sometimes you may end up seeing persons do this, but this is what we call a magic string. And it's usually discourse because you could make a simple mistake and not realize and it would be very hard to figure it out later on. So we need to stream dot empty. You will let see sharps at the value for you. And it will be much easier to maintain and on track, don't. Let's see age. So I wanted to edge, I'm going to use an integer because people generally would be 2021, not necessarily 21.8 years old. I would want an integer instead of a double or a float because I'm not expecting a decimal for this. You can also assign this one a default value. I'll just set 0. There are defaults here, but you would end up being int dot, max or Min, which would be on either scale of billions. All right, So Min is minus 2 billion or 2 trillion or something like that. I mean that mux is positive, that same number. So here I'm just going to set that default is to 0. Maybe one, maybe a default ease off one makes more sense, right? But hey, next stop, salary. No salary. You could expect that decimal points because salary represents money. You could use double. Then if you wanted to make a default equal to 0, that's your default. You could probably also see float does that also takes decimal numbers, except the default value has to look a bit different. So you'd have to see something like that. 0 f. Just to show you, I'm just showing you the nuances with a different datatypes, but this is also a decimal place is just saying that you have to put on the F to represent that it's a float and not just a regular double. You could also use decimal. And if I'm not mistaken decimal, you would just see like 0. You'd have to put on suffix m. There we go. Once again, just showing you the different options, different nuances. Alright, so I'm going to keep it simple. Door double is good enough. And I can just say that WE will know that it's a decimal, so 0 is the same as 0. Gender. No, I would probably want the user to enter M for me, F for female. And then you'd want to use a character for that. So I would say char. Notice I just accidentally wrote a capital C. Capital C char is different from common CHR. Similar but different purposes. So you always want them to be lowercase when you're defining your variable types. Char and gender. I can initialize this one tool. Don't think that there's a char dot empty. We do have Min and max value, and you have a number of other operations. They're not going to go through all these operations just yet. All right, so here I'll just say give me the mean value for the char. Then it's asking for birthday. I don't want birthday this time I want Boolean. And are you working? So Boolean here represents true or false. You either are already, aren't you? You're either on or off binary one or 0. Bool represents that binary decision, that binary value one or 0 true or false. The working or not working. Here, I'm just going to default to false. So you'll notice that false untrue are actually keywords. You can tell that from their color coding and the fact that results through it is actually suggesting those values in the IntelliSense. For me. Even with a bullet, if I don't assign a value, it will default to false. So that's something that you can bear in mind if you don't give it a value, it's default is false. If you don't give integers and doubles values, their defaults will be 0. Char that will default to null just the same way that the string will default to null. As you practice and you get more comfortable. You will know these things. I'm pointing them all because I've been doing this for years so I can exude this wisdom because of experience. Both I'm shearing the wisdom so that you can have it in the back of your mind when you're going through an experience. So those are the variables that we want to work with for this exercise. Know what I wanted to do is prompt the user to enter each one of these, and then I wanted to store it in the variables. Let's start off with name because we've done that before. So I went to see console dot write line. And I'm going to say Please enter your name. I'm going to do console dot write. I wanted to talk to print in one line and then it's going to pause for input afterwards, semicolon. And then I'm going to see that the full name is going to be equal to whatever the user inputs, which would be console dot read line. So remember that last time we looked at the fact that you just have to assign it there. No. I didn't mention you could defined a variable here and do everything one time. For readability purposes, sometimes it's good to just get all of your variables defined up top and then you use them later on. So at least you know what you need. Then you can write code our own what you've already worked old. It's not necessarily one is better than the other. It's just, I'm just suggesting this kind of workflow so you can get your mind in order and have your strategy for your application ready for when you need it. This section, I'm just prompting the user for input. Know, I'm going to basically just copy and paste this and I'm going to say please enter your age. Sometimes you have to work smarter, not harder. You already have the console dot write line. You know that you need to assign the variable that I'm going to do is copy and paste. It takes its end needs to change and then use the appropriate variable. So here I'm saying give me the age. Wow, no average. What is this red line thing? It says it represents sorry, let me hover over this again. Okay, So sometimes when you hover over it, you're not going to see the error. Oh dear, it is done at end. Cannot implicitly convert type string to int. So please you can go to see the error details would be error list, which is usually done at the bottom part of your interface cannot implicitly convert string to int. And if you don't see it there, you can always go to view. And you'll see error list and you click it and it will appear. Here. It is saying that I have an integer called age. But console dot read line is actually accepting a string from the user, meaning no matter what I type in through the console, it will always see it as a string. So remember earlier when I discussed the different datatypes, I had said that the string is actually capable of storing words, numbers, special characters, anything, anything that is on your keyboard is actually going to be processed as just one big block of text. When we put it in the console input, it is not assuming that because you put the numeral one, that you want an integer r, you put one letter you want a character, or year-old award truly meant a Boolean. It will always be assuming that you are entering a string. So if you want this string to be stored as something else, we have to do a manual conversion. To convert from string to int. You have the option to use converts, which is just another built-in class. And I can say convert dots. And I can see two in 32. I wanted to convert in 32. This is a method, so I have to open my parenthesis and then notice it's seeing after parsing that string value that I intend to convert, what am I converting that string input from the user. When we just say convert to in 32, whatever input came in from the user. And then every time I open a brief so r bar and the SCC, I need to make sure I close it. So this one, this one is open-ended loss for, for the red line, but I need to close the 32. There we go. That gets rid off all the arrows. I hope that was clear. If it wasn't clear, doubled to get much clearer. Now we move on to salary. So I'm just copying and pasting again. And then I wanted to say Please enter your celery. Then I'm going to be assigning salary. This is converting to 32. I don't necessarily want to 32 in salary because salary is a double. It is not an integer. So I don't want the person putting that they made $210.05. I don't want just $210. I want the five-sevenths also say I need the decimal place. Well, guess what? I can convert from string to double our two decimal, we're using double, So I'll say to double. There we go. All right, so string input from user, convert it to double storage instead of salary. Coming along nicely. I'm just going to go ahead and duplicate these lines for gender and working and we can figure them out. Gender these into the gender. And then please enter if you are working or not. Notice red lines again. This one says Gender. This one says working. Let me see it. Working status. Let me rephrase that. Are you working? Are you working? All right. So forth, agender, we're using a char. I know needs to tell the user watts legitimate inputs hour or what the inputs are that I'm looking for. So I'm going to see inside of the prompt message M or F, enter either one of those letters. Then went up to convert the string into character. Goes around about character is different from a string because this can have multiple characters in it's contiguous block versus a char, which is literally just one character at a time. So I went off to see converts, Dots, tool. And then I pause in that string inputs that hopefully only has one of the choices that I've presented. And then I'll store that in gender. Likewise, are you working? What do I expect the user to put two in? I expect them to put in true or false. Why? Because I just wanted to add direct conversion from the word true into the actual datatype. That is a bool, which is the keyword true. For our visual representation. True in quotation marks. That's what's coming in through the console dot read line. But I need true. The keyword, which is what I would say until Boolean. We're going to do with that convert tool. Boolean. I'm sure Visual Studio is giving you some good suggestions because it's contextually looking at what you're trying to assign this value to. So it would suggest to them, because clearly you're working with a Boolean. This is it for prompting our user and for behind the scenes converting whatever the type from the default string into the actual data type that we need for our background processes. Using the correct data type is very important because. If you need it to do math with salary, you cannot do that kind of math with a string. You have to have it as a numerical value to see if this is what you earn per month, then this is your ear, the salary, right? So if we ask them to enter your yearly salary, I wanted to show them what they earn per month would have to get it as a number in order to do the math. All right? So those are the things that you have to consider. At the end of this, we want to print the information back to the user. So we wanted to print out this is what you entered, here's what we have for you. So I'm just going to see console dot write line. We know that we have to do that. No, at this point, I can do what we'll call concatenation. So I went to see your name, is. I have two choices. I can't see your name is and then have another console dot write line were printed full name. This is what we did last time. Then that's going to end up doubling up in every print statement when I can do it in one line. So your name is, and then I'm going to do what we'll call concatenation. So I'm going to say plus and then give it the variable. What this does. It says, please add this block of string. This is a literal because I, the programmer typed is so this will never change. Plus whatever came in through the variable because I don't know what the user is going to be writing in. That is what we're doing there. Another way to write this or to do this kind of concatenation, let's say with EJW, if I wanted to see your ij is all right, I can actually put a placeholder here. So I went to see open curly brace 0, close curly brace. And then I'm going to put in the variable that matches. So I can see each know what this is doing is it's actually creating what we call args. So our arguments that will be passed into the function. So the arguments will be boned to the variables that go into see him order. So if I had multiple arguments are multiple variables that needed to print, I could actually just do 12. And then I can see some text here because I'm writing with a whole sentence, but parts of it needs to be dynamic. I didn't for each of these, I'm going to call them placeholders. I would provide a variable in the same order. 0 always goes first. The first variable matches the 0. The second variable, much is still the other one, etcetera, etcetera. All right, so I will just list out as many variables as I have placeholders. So that's some other ones. I'm going to keep this one simple. And we're just going to see your age is then we're using placeholder and printing each. Another way to print what we call concatenate string would be to see your salary is. And then I would put the variable here. Instead of seeing please holder, I would see curly brace and then put in the variables, so celery, but notice that everything is still Orange already in the same color as whatever your string literal representation is. What's missing here is the dollar sign. I need a dollar sign before I write the string. Then that allows me to use curly braces and super impose the variable anywhere in that stream that I want. This is called interpolation. So this is concatenation. This is called inter pull leash on. The thing with interpolation though is that inside of this string it's very similar to using the args. But I can actually just sprint the variables where we'll say if I write something takes, I didn't, I wanted another variable and then more text. So I'm just writing all to one block gloves string, but anywhere I need it to be dynamic, I just write in that variable accordingly. Prints that string. It will just putting those values wherever I stated the variables should be. All right. I'm leaving a little comments. They are aware of what's happening at each point. So these are all of your options when it comes to printing and interacting with a string on the variables. C-sharp does a good job of changing everything to strings. So you have to be deliberate to change these into whatever datatype because it's going from string, you have to be deliberate with the datatype you're converting tool. However, you would notice that I'm not converting anything else to string here. This is a string and I'm putting in a double inside of a block of string. The same thing here with edge will full name is already a string. So here it will always convert whatever data type it is into string without you having to do anything else. But if you needed to, you could always say variable dot toString, which will also convert it to strings. So that works, but that's kind of redundant because it's not needed. Because C-sharp is that blue. I'm just showing you your options. So let me just duplicate this and see your gender is, and then I can just put in gender. Then I can see you are Floyd Are you employed or you are employed? Sorry, I'm just getting caught up in altar write this, you are employed and then I'll just see working. Alright, so it will automatically convert it from Bool string for me. A lot of the times you'll see me doing this, but later on we'll look at string manipulation in a bit more details. So I'm just showing you some options here for us to get through this activity. And later on we'll delve more into what is possible when it comes to strings and different data types. From here, if I wanted to run this application, once again, I have to change it to that project that we're working with, variables and data types. And then let me execute. Then let's start filling this out. So this is going to be test name. Enter into your ear edge, let's say 23. What is your salary? That's a C. I am earning that 0.35. What is my gender? I went to state the ones that I was suggested to stay it. Then on my working I am working true. So at the end of it, you're getting your name, your age, your salary, your gender, and you are employed. No notice there is no space here. Why is there no space there? Because I have a dipole as you can just fix that typo and that would fix that printout. But that is really all that I want us to go through in this exercise. We looked at the different variables, at a different variable types and whole weekend give them the default values versus non-default values. We also looked at the fact that we can or we need to, when accepting input from the console converts to our specific datatype based on what we need. And we also looked at the different ways that we can handle printing old static text combined with Takes coming in from our variable. 11. Application Debugging Techniques: All right guys, so in this lesson I want to discuss application debugging techniques. No, debugging has to do with finding errors in your code. At this point, I have a bunch of other projects that we will be going through one-by-one later on. So don't get caught up on the fun that I have many projects and you don't let us focus on the project that we just completed, which was looking at variables and data types. And I wanted to show you how you can try to find errors in the code as we go along. All right, So we have different kinds of errors that will appear in our code. The easiest one to spot is a syntax error. Syntax error could be as easy a type or you would have seen that they wrote a few wrong lines. Sometimes, if I wrote console instead of console, then the syntax error would be apparent through the prison itself, the red line, we've seen that before. You'll also notice that Visual Studio would kind of highlight the lion to your right. And you'll see that little red square up here showing that there is an error on that line. You'd also see that you have that little x down here and error list will be populated. So there are so many indicators as to the idea of an error in your code when it is a syntax error that it's hard to not notice. Now let us say a prayer adventure. You didn't notice it. And you tried to execute someone to change my starter project here. Then I tried to execute this. I didn't notice that that syntax error and I tried to run, then I'm going to end up with an error like this. So when you run, you will have two options. You have run with debugging and run without debugging. Running without debugging means that it's just going to build, make sure everything is okay. And then tried to launch a program written with the ballgame means that it's going to run, but be mindful of the fact that you might want to track what's happening. So we looked at that in a few. However, neither option will work when, if you have a syntax error. So when you get that kind of error message saying that there was an error with your build. Do you want to continue with the last successful build? You don't want to continue with the last successful build. It means that you're going to go back to the good version of the code, which would defeat the purpose of writing new code that you're able to test. You want to see NOR. And then he wanted to give some attention to your error list so it can show you where your errors are. So just by double-clicking here in the area of the city will actually jump to that line with the errors. Whether you're going to fix it, commented or whatever you're going to do, just remove the syntax errors. So those are the easiest errors to detect. Know the more difficult type of error to detect is a logical error. In logic error can be because you didn't write the coordinate particular way you did something before he should have done something else. Remember that we have sequence, we have her position and then we have decisions. If you're a sequence was incorrect, then you might not get the desired results. If you made a bad decision, meaning you wrote a statement condition incorrectly, then you may get a bad results there also your for-loop, etc. There are a number of things that can throw all the logic. Those are logical errors which really manifest themselves during runtime. One of the ways that you can use the truck values that are being assigned is by sitting in what we call breakpoints. Breakpoint is let's say a marker line of code that tells the compiler that while you're executing all the code, when you hit this line, I want you to pause. Let dot-dot-dot register for a bit to get that break point. If you look to the left of the line numbers, so you have the editor, then you have your line numbers, which when you click it highlights the entire lines you'll see me doing That's a lot. To just get the entire lining just clicked that line number. But into the farthest left you'll see that the cursor inverts again. So here it occurs, so it looks normal, just a regular pointer. And then when I go over to the line numbers, it becomes kind of pointing inverted to the next direction, and then it goes back to normal over here. And then you'll see those little white dots appear on the lines of code. When you click where that dots up here is, it turns red. The red dot signifies a breakpoint and that entire line turns red. So you can have multiple breakpoints. Throw it to your code. The activate the breakpoints, you just click it again. Click to turn on or turn off. When you are running. In debug mode, meaning you press this bigger play button or you hit F5 on your keyboard, it will run. And be mindful of the fact that there might be a breakpoint. So when it hits that break point is going to pause. When it pause it allows you to interact with the variables and other bits of code that would have preceded it. If you run without debugging, then it will just run. It won't curable at the brief points. Let us run with debugging and look at that experience. Here you see it. Seeing enter name so that we know what that we're at 912, That's where it's waiting underneath to go in. I went to put in my name, press Enter. Then it goes over and asks what they eat so you know what that is? No outline. 15. It's waiting on the edge. So putting an edge and then look at that. So it printed the prompt for a line 17. Body can't go any further because of the break point that we had put that line 18. Know the obligation is actually stopped no matter what I do, I'm actually pressing keys are, and no matter what I do, I move forward because the compiler won't allow me to. Alright, at this point, if I hover over these previous variables, I can actually see what values went in and I can see that full name currently has a value of Truvada. William's age currently has a value of 25 and it's waiting on salary to get its value. And salary currently has a value of 0. Gender has the value of 0 slash 0. That was the mean value. And working by default has a value of false. See that? Just by hovering over them, I can see that. I can also go down here where the some of the additional toolbars are and I can bring them up. I'll watch, watch, that's tiny. The watch section allows me to put in a variable second and watch the gender variable. And it was showing me what its value is. I can watch full name. And it was showing me what its value is. And I can also watch salaries. So let me watch salary. No salary has a value of 0. But if I press F9 on my keyboard or if you live in, and I have to make sure to press F 11 because f ten will actually stop the recording for me, the difference between f ten and if we live in, is that if ten we'll skip over a method, whereas FLM will bring you into the method. Later on when we're writing code together, we will see that working. But for null, if ten or 11 is fine. So if I press F 11, it will move on from that breakpoint. And all the numbers, these are all the numbers I was putting in earlier. But no, it's actually at line 18 waiting for me to enter something and press Enter. So if I put 800, let me erase this and just put sensible number and then press enter. It will move on to the next line. So you see when it hits the line, it changes it to yellow. When it hit the breakpoint, it was yellow when he moved to the next line. It's not showing me That's how about the next line? Right. If I go to the watch to watch his nose showing me that the salary is no longer 0, it's not 8 thousand because that's what I entered. At this point. I have a few options because it's still waiting for me to go line by line so I can continue to do F11 or f1 until the end. Which I mean for a small program like this wouldn't be a big deal. But sometimes you really just wanted to devaluate what happens at a particular line. After that particular line, you can let it continue. To let it continue. You just press F5 or click Continue up top. And once you do that, it will just continue with the execution of the code as usual. So here I can put in m and you see it's not pausing and asking me for anything and it continues to the end of the execution. Once again, this breakpoints allows me to pause the application in its trucks. And I can take a look at the variables may be whatever it was being set was incorrect, maybe the salary value was wrong because the calculation is wrong. This helps you to pause your application and take a look at the values that are coming across. And then you can determine that, okay, maybe I need to tweet this or modified that as you go along. And then it helps you to move forward. Here with celery, I just disabled the checkpoints are at the breakpoint rather by clicking the red dot and clicking it off. You cannot have multiple. The point is that each time you hit Continue, it'll go as far as the next breakpoint in the line in that order. So if I enter the salary and it went here and in that pressed continue when he teaches line 20, he would continue, continue, continue. And then it would do everything up until the next break point where it pauses and waits for me, the developer to either evaluate what's happening and then continue or go line by line. So that's some guidance as to debugging in your application. This will come in handy. When you end up with errors. Maybe your logic is not as well thought of it as you would like and that happens, we're all human, right? Sometimes you don't get it right the first time. Which is why these tools exist to help us to refine what we're doing. 12. Arithmetic and Assignment Operators: In this lesson, we are going to be looking at math operators, lets us create a new project. And we're going to be calling this one math operators using dotnet six. And then we can get this show started. No. We want to look at maybe three categories. We have basic operators, are basic assignment operator. Rather, we have arithmetic operators, operations. Then we have maybe compound assignment operators. We looked at the assignment operator before. This one has to do with assigning a value int num, we have a variable. Cool. I want to give it a value. I'm going to say num is equal to maybe five. That is called an assignment. In regular English or irregular math, a human being, when you see the equal sign, it means that whatever is on the left has the same value as whatever is on the right. However, in programming, when you see one equals sign, it means whatever is on the right is being assigned to what is on the left. So this is our variable. We're assigning the numeral five to the variable. That means the reverse won't be true if I write this in code, I'm just going to get an error because there is no way. I'm seeing that these two are equivalent. In regular English or regular human language. That would probably be acceptable, but not in programming. Already explored whole, we assign values, our variables. And if we wanted to do it in one line, we can easily just say int num is equal to that value. By default, once the variable is created, it's created with that value. Now let's look at arithmetic operations. Arithmetic operations would have to do with us doing math. I'm going to do norm1, give it a value of something random 11 and num2, Let's give it a value of 12. Thank you. Visual Studio. You see here, he's just a gift that keeps on giving. However, that's not what I want this time. When we wanted to do math, we have the opportunity to do the same kind of math that we're used to in our regular daily lives, right? So if I wanted to do addition, remember I said that you can do different operations. We can easily add num1 plus num2. Simple math. If I ask somebody if I wrote a program for calculate and that's a nice activity for you. Write an application that accepts two numbers and performs addition. You would ask them to enter into num one and turn it into num2. And then you would see num1 plus num2. Then proprio have another variable, int sum is equal to num plus num1 plus num2. Math is that simple? So I'm just going to write them inside of these Console.WriteLine line. So we actually print them back to screen and useful lines of code. That's a nice activity if you wanted to go on right, and a calculator after this activity, then that would be a good practice for you. Writing input, output, and processing applications. We can do math, we can do addition, we can do subtraction. Instead of a plus sign. We have a minus sign. We can do multiplication. So remember that I'm just duplicating the lines using Control D on my keyboard or Control CV. All right, So multiplication is represented by the asterisk, not by the x. Alright, so we write an x when we're doing math, but it's an asterisk. In programming division, you don't want to have a division symbol on your keyboard if you wanted. That's in Microsoft Word, That's a special symbols, so we use the slash. So that's a division sense. Norm one is being divided by dome tool. If we want to do modulus, we use the percentage sign. Modulus is basically the division or the remainder after division. So let's see. Two divided by three. Divided by three is going to give you something like I'm sorry, let me see. Five divided by two. Let me do something more easy. Five divided by two would leave, would go into two times, remainder one because it would get a superinfection. Well, you'd get two times remainder one, tool times remainder one. All right. Now, if you wanted that remainder one only, then you would say five modulus two. That will return just the remainder. That's what modulus dot. So if you've never interacted with more details before, that's what it does see if you ever get to an application where you need to find all of the odd numbers, are putting a number and find out if it's odd, then pretty much if the number, let's say I'm sorry. I think that would be a nice activity for us to do after this. I'm going to leave that until later on. But if you ever have to find out if something is an odd number, all you have to do is do number modulus two. And if whatever the result is, is one, then it is an odd number, right? That's all modulus works. So let us, in a bid just to drive the point home, I'm going to modify the value of num one. Num one. Your new value is norm one plus four. All right, so that's me increasing the value of num one. And then if we were to print out all of these and I'll just add one here to see a new value of num one is whatever norm OneNote has. Afterwards then you'll see that these were the original answers. I modified the variable's value and then we get these new values afterwards. That's a simple math operations. Then you have different libraries that allow you to do more complex operations. Tangent and sine and cosine, etc. But I'm not getting into those in the B6 right now. If I run this program once again changed the car starts or project to math operations are operators started the project, it should just spit out all of these calculations. So the console screen. There we go. So sometimes the console will pause. You just have to click. If you click in it will kind of pause. So when you press enter it will continue. So here we have the addition and subtraction, multiplication, division and modulus. You see here it said that 12 could not go into 11, right? Or what was that? That was normal one does he live in divided by 12, so that's 0 times over the modulus is 11 caused the remainder would be 11. Then we go onto new value of norm one is 15, and then we get the addition, we get the subtraction will go into multiplication. Know, 12 into 15 goes one time. If the remainder is three, modulus gives us the remainder. Alright? That's really it for basic arithmetic operations. Node compound assignment operators would be like a shortened version of doing something like if I wanted to modify the value of a variable, but I wanted to add or subtract from the original value. In this case, I increased it by four. So I said whatever the value of num one is, right? No, give it back to me and add four and then assign that new value. Normally that's installed, I would increase it. If I wanted to decrease it, I would just do the same with a minus sign, etc. If I wanted to make it four times its original value, I'd say multiply. Now when we talk about component assignments, it would be a shortened version of doing this kind of operation. So if I wanted to see increased num one by four, I can see norm one plus equal. Then give it the value. So this would no see accumulate. So we have this, this is called an accumulator. Norm. One increases by four. That's pretty much the same thing as writing what we did up top here. I'll just come in adults. Same dynamic. Alright? And then based on what you want to do, like I said, if you wanted to decrease by four, it will be to see him. I say num one minus four. If you wanted to multiply it, make it four times its original valid. And it will be times. If you wanted to make it four times less than its original value, then it will be divide, etc. So when we talk about compound operations, That's what we are doing. Compound assignment operations. The thing is that with each of these operations, we're actually changing the value of num one. So it's not a matter of just printing out, this is the result of the operation, it is actually changing. So here I'm seeing odd for me to remember what sequence. So num one starts off as 11. We go through all of this or the sprinting, all the result of the operation. We're not assigning anything. We're not making new variables are assigning any value to any variable, then I see increased normal one by four meet that the new value, num one at this point is no longer living, it's now 15. So all of these math operations are relative to normal one being 15 and num2 still only being 12, which is why we saw the different sets of results at this point normal and is still 15. When I say plus equals four, I have no increasing it from 1519 causes at this point it is already 15, so I'm adding four to 15. And then here I'm going to say make it back 15, right here. I went to see if 15 times four is equal to 60. Know no one has a value of 60. And then here I'm going to say divided by four, I'm putting it back to 15. And then I'm going to say modulus four. So that means 15. Modulus four would be if my math serves me right three. So what we're going to do, just to test if my math is still on point. I am going to do our console dot write line. And I'm going to be printing the value of num one with each operation. Then we can compare to see if my mouth that I have in the comments there would be correct. Alright, let us run this application again. Alright, so now it's your time to mark my math assignment. So I did say that the first one to Ockham will be 19. There we go. The second one to o con would be 15, then 60, then back to 50, and then the modulus would be three. So no, each time we're changing the value of num one. That's his whole, you can go ahead and modify variables. If I said increase something, increased all the prices by five, then you know, you can just see price times z equal five. It would automatically do that. 13. Conditional Statements: All right guys, In this lesson we're going to be looking at conditional statements. I've already created that project. By now. You should be familiar with how to create a project. So you can just go ahead, hit pause and go ahead and create that project. When you've done that, we'll continue and we're looking at conditional statements. Once again, with conditional statements, it's all about making a decision. We already discussed that we have sequence, we have decisions, however, repetition. So decisions on conditional statements seem. So we have basically three main ways of making decisions in most higher-level languages. So when I say high level languages, I mean C-Sharp, Java, C, C plus plus, and languages like Python, Ruby, etc. So we have if statements, we have switch statements, then we have Turner operators. The syntax off course would differ, but generally speaking, you statements, switch statements, and ternary operators. They all look the same way. The same way really in CC plus plus C-Sharp Java. They may have slightly different interpretations in Ruby and Python on certain other languages. But once you understand the general idea, adopting to another language is really just a Google search away. Even though I'm doing a C-sharp course, I just wanted to bring you to the points of realization at once. You appreciate these concepts within C-sharp, they can be applied to any other language as you may need. If statements generally make use of what we call conditional operators. So we just looked at arithmetic and assignment operators. We looked at conditional operators. Conditional operator we've seen one before, is in the form of a w equals sign. That one means equivalents. So like I said, the, the single equal sign doesn't mean that the two sides are equal. It means I'm assigning what's under right to what's on the left. However, when we see the double equals sign, it means that whatever is on the left is equivalent to what is underwrite. That's an equivalence operator. They also have less than, we have greater than. Sometimes I get those mixed up, so just work with me. We have less than an equal to. We have greater than and equal to. We have not equal to, which would be not the equal sign symbol. Those are generally the operators. And once again, those are in most of the languages that I had listed out earlier. So once you understand how to use these, you can apply them almost anywhere else. So let's get started with a simple program to see how this works. I'm going to say int num. I'm just going to prompt the user for input. So I'm just going to say console dot, write line, enter, first number. And then we just see int num is equal to converts. And I'm just going to write everything sharp because we know what we're doing. And it's even Visual Studio is helping me out. So whereas seeing into your first number. And then we're going to convert to in 32, whatever comes into the console. And we're missing a semicolon on that line, which is why I had that red line there. Alright, let me see. Visual Studio is going to have to again. No, that's not the hip I was hoping for us. So let me just copy this line. I went to call this num one. I don't want to call this num2. And I'm just going to say Enter your second number. We're asking the user for a tool numbers. Now, let us look at some conditional statements that would be sensible. So what if I wanted to know if numb one is greater than num tool? I would start off and say if which is a keyword. But notice it's not a statement because I don't need a semicolon on the end. So I'm going to say it's suggesting num one is equivalent to the norm to what I'm not there yet. So I wanted to see if normal one is greater than num2. Then I went to start up a code block. What would I like to do? Maybe I would like to see console dot read line. You have, you know, let me, let me make this a bit more context or enter number of apples. Num one represents uploads. I didn't. Here's an example of me violating my own rule. Num one does not tell me that this is storing upwards normal one here says number one, what I'm asking for uploads. So there's a disconnect here, so it's better, I would name it number of apples. So it's clear. Now when I name of rename a variable and I have to rename it in several places. Of course, I can just go through and copy and paste or I can just do Control and dots. And then you'll see the option Rename. From old name to new name. When I click that, it will just go through and refactor all of the parts for me. That's a nice productivity tip for you. I want number of apples, number of oranges. I went to call this one number off oranges. And then I went to the same control dot and renamed NOW number of apples, number of oranges. If the number of apples is greater than a number of oranges, then I went to see you have more couples. Cool, nice and simple. All right, That's a new statement. But what happens if I have something else I wanted to check for? Because this is only checking for one-off the conditions and it's taking one action, one-to-five more orangey is then I've upwards. Then I can say else. This would be like if this is the case, then do that. Otherwise, do this. I'm going to say you have more oranges. If the number of apples is greater than the number of oranges, then you have more apples, else you have more oranges. But that might not necessarily be the case because what if they're equal? Because right know, I'm only checking for one condition, alright? And explicitly, I'm only seeing if the number of apples is greater than this, then this, that's not a fair assumption because I could have the same number on either side would have to introduce more conditions to this hole. If check, I can actually have another construct called L, which allows me to check for another condition. I can see if this is the case, that else, if this is the case, so number of oranges is greater than, number of apples. Or I could see less than, so I use a greater than already. So let me see. Number off. Oppose is less than the number of oranges. I'm just showing you how to use up the conditional statements. Operators, LLC. If the number of apples is less than the number of oranges, then we print you have more oranges. What if they're equal? I can do another one else. If number of Uploads is equivalent to the number of oranges, then we want to write some more code. I notice that it's not illegal for you to put the else if on the same line as a curly brace. I'm, I tend to speak the model because I want that clear distinction as the weird one starts on one stops. But it's not the LIGO to write your code like this. Else-if that is the case, then I'm going to console that. You have the let me just see the same number of apples and oranges. That's what I went to print to the console. It's one big decision. So you see you can have a simple decision. You can have complex decisions to make based on two different variables and different things that are being thrown onto two different considerations and really enjoy it. That's all big obligations. Are there You statements? If you do this, then you get that result. That's all that they are. Now wants a whole company created the application may seem whole beautiful user interface is and how high ticket looks. At the end of the day, it all comes down to a bunch of if statements. If you press this button, what do I do? If you put in this value, what do I do? That's all it is. All right? So at the end of all of this, if none of these conditions holds true, then you can finally make one big else statement that would see invalid input or could not compute our direct action. You don't want something like that. When you get those, when you put in a certain volume and an application, I get something to say that's an invalid value. It means that all the if statements that were written did not account for what you actually ended up putting in, it'll sit else. I don't know what to do. I can't I can't help you. Alright. What's in this situation? We probably don't need to go that far, so I'm just going to remove it anyway because I think we're covering all the potential outcomes based on what we're asking here. The number is either going to be greater or less or equivalent. Granted, you could put in all the ones I created an r equal or less than an equal, etc. But we're not going to go into all of those. Just know that those are options. And it obviously, if it's not equal. Then it's going to be either greater than r, less than that. So you can make decisions when you are at in the code that you can make a decision as to what kind of decision. Our conditional logic you need to put in to match the situation you're dealing with. You can go ahead and test that one if you want. You can put in the same number, you can put in two different numbers. And based on the numbers you put in, make sure that conditional statement is sprinting what you're expecting. I'm going to move on to switch statements. You can hit Pause, go ahead and test and experiment, but I'm moving on to switch statements. So let us see that we have, um, we need to evaluate watts is in a variable, and then based on what is in the variable, we need to take on oxygen. Alright? So I'm going to give you another example that I think is practical. I'm going to ask for agreed. Alright. I went to see enter final grade and we're going to determine if you passed or not. Someone to see integrate is equal to whatever is passed in through the console. So a switch statement literally starts off with the keyword switch. Then we put in the variable that we're going to be evaluating grade. This is not limited to integers. This can be with stringy, can be with charge, can be with anything. Because even when we're accepting the form and we said MRF, I could have easily put in a switch statement R&D if statement to see if m then print meal, if F then print female or switch, similar to what we're able to do. So I'm just showing you that it's not limited to integers. I'm just doing this room. So I can say something like the switch, I can specify a case CC or Visual Studio is waiting for me to pick up. And continuous I can say case 0. What do I want to do? Console dot write line, you failed. Nice and simple message. Then I need to end each case with outbreak. Pretty much that's it. All right. Whatever you do between that colon and the keyword break is what will be executed if that is indeed the case, where we're looking at the value of your grid. Grid probably wasn't such a good example because the case has to be very specific. So unlike the if statement where I could see like this greater than that or the scripted and that's that I have to be specific with a value. So I can only see keys 0. In that case, I can say keys one or tin. And the ofcourse, whatever value I use is relative to what I'm checking for. Here I would say Console.WriteLine, you got ten marks. If the value is ten, then it will go here. If the value is 0, then it will go there. But if it's not ten, it's not 0 and it's a valid that is not accounted for in the cases, then we would want to give you that default. So default means this is what I'm going to do when all else fields. All right, so break, Console.WriteLine, invalid grades. So if we entered 1 thousand I, we did not go on for dot 1 thousand inside of all of this, then we would just go to the default that would be like the default else statement, the catch-all. No other condition was met, so just do this by default. That's what the keyword is here. If I wanted our range inside of my switch statements, which would meet more sense here, considering that degreed is usually between 0 to 60 for the failure and then 6060 to 100 for the pause. And then default would represent anything outside of 0 to a 100. Then you'd probably want to do something like keys, int. Just choose a variable when. Then you can see here is, let's see, great today. Sorry, less than or equal to the value of 60. All right. This point that just escalated, right? I'm sure you already understand how you do keys against a single value. If you wanted to check 102030406998, you just have keys ten, right? What do you want to write? Break, case 20, etcetera, etcetera. And you'd go along, if you wanted them to share the same block, then you would actually just say like keys 101112 and All of these cases would just use that one block of code. So yes, it's unblocked, but there is no open and close parentheses like you have to switch. It's just the colon's. So all of these would actually share whatever happens here before that break. That is one way to make different conditions for different values share the same thing. Of course, that will be tedious if you are checking between 0 to 60 because it would mean you have to have 60 cases. Are 61 case is 0 to 60 to check for failure. That wouldn't be practical. What I'm showing you now is how you can make like our range for a number of values. Right here I'm going to see case. And then int n. So n is like in in-process representation of the value that we're evaluating. And then you'll see when I actually think these braces are optional, if they are int n, when this n, whatever n is, whatever that value is and represents that value is less than or equal to 60, then you print, you failed whatever value. And once it is less than or equal to 60, then you field. So that I can now check case int n. When n is greater than 60. Then we can say you passed. That makes sense. So 60 is the pass mark, you feel are 61 is the password, let's say greater than or equal to 59. Yeah. All right. See if it's greater than or equal to 59. Less than or equal to 59, sorry, That means you've failed. However, if it is greater than or equal to 60, then you pause. So 60 is the pass mark upwards. However, if I put enough thousand, that is not a valid value. So there is another situation where sometimes you need multiple conditions on to seem multiple conditions thrown in the same decision. All right, here we have to use what we call the and operator. And operators would be, and they also have our operators which would be RR. So that's, these are pipes and these are ampersands. Alright? So anytime you want to specify two or more conditions within the same decision, like for this case, I wanted to make sure that it's greater than or equal to 60. It's also less than or equal to a 100. So I can see when n is greater than or equal to 60 is less than or equal to a 100. I didn't Standard English. This would be like saying between 6100. That's what the Andes, alright, so when it is, as it's over 60 but also less than a 100, inclusive of these two values, then we can bring to you passed anything outside of that is an invalid grade. So my challenge to you would be to modify this to make sure that it's creates a non-zero. It's not negative. Negative would be invited over a thousand is invalid. So that's my little challenge for you based on this example, modify this case statement to make sure that it's not less than a 100. Like I said, you can have as many statements in this section as it needs to. So if you wanted to print you pass multiple times, as long as you do that before you hit the break, then you have no problem. That's another way to make a decision inside of our C-Sharp application. The final one is a ternary operator, which is like a one-line version of a simple if statement. Let us say that I wanted to determine the message to print based on the condition here. I could easily say something like message. Let's say var message is equal to. And then I check the condition. My condition would be if number of apples is greater than number of oranges, then I want to make my message b. You have more apples. Otherwise my message will be you have more oranges. There are so many ways that you can do this. This turner operator can come in handy in so many ways. I need to just print the message instead of having the whole if statement here. If and else if you could just have a turnoff burrito, no downside. So I'll turn our operates as simple as it is, is that it's generally designed to just have one condition so it wouldn't get complex as a whole. If block that can give you multiple variations of different old columns, etc. He would just be like, is this condition true or false? If it's true, denoted by the question mark, then this is the value that I want to place inside of this variable. If it is false denoted by the colon, then that is the value that I'm working with. And that pretty much works anywhere. If I wanted a Boolean, what I would need a ternary operator for Boolean. That's an activity for Leto time. Now I gave you a challenge to modify this to show the range. So what I would've done here, we'll say int n, when n is greater than or equal to 0, is less than or equal to 59. And that's it Really. This is between 059, you failed. Between 100, you pause. And then like I said, you can have the keys would assemble. So let us see. I will just show you, leave you with an example of a simple case. Let us say k is 101, that sees the value. And then I'm just going to say console dot write line. Single case example. If you did cases 101, that's a single case example. That red line is there because I need a break. All right, So every case it needs to be followed by a break. You can go ahead and run this application. We're going to be prompted to enter two values or I'm sorry, I'm still under the wrong one. So let me change it to conditional statements and try that again. Then we have to enter the number of apples, someone to say ten, and then a number of oranges on what you see at 20. And then I'm getting the message. You have more oranges because the number of oranges was indeed greater than the number of art was, the number of apples was indeed less than the number of oranges. So I have more oranges right. Now, if I enter the grade, I went to enter 50, then you failed and didn't know. Well, that's the message from the ternary operator. Let me just comment that ought to avoid any confusion. But let us try this again. If I enter ten for both apples and oranges, 1010, you have the same number of apples and oranges. Thank you. And then if I enter 101, it is going to say single case example. One more test. I'm just going to comment out the if statement operations run without debugging, so it loads a little more quickly into final grade. If I enter one falls under something greater than then it's going to see invalid grid. Couldn't meet that case. It couldn't meet that case. It didn't need this case, so it went to the default. That's pretty much how conditional statements work in C-Sharp. 14. Repetition Statements: Welcome back guys. In this lesson, we'll be looking at repetition statements in C Sharp. No repetition statements generally come in a few forms. We have a for-loop, we have a while loop. You have do while loop. You have others that I'm not willing to explore in this particular lesson, but I will make honorable mentions off. And that's namely, well, before each loop. Lets us focus on the ones that are generally prevalent in general programming. Once again, I'm always trying to show you how to briefly give off a whole to apply what you're learning here in C-Sharp in any other language. For loops, while loops do while loops, those are available in every other language. The for-loop is what we call a counter controlled loop. Basically means I am going to loop for this many times. So there's a counter that striking how many times you did already run and how many times it needs to run. Then we have what we call the condition-controlled loop. This one is a pre-check, meaning it will check the condition. So we just looked at conditions resolved or at conditional statements. So it's going to check up on Deshawn. And then if that condition does not hold true, then it will go ahead and do the loop. And it will keep on checking the condition until it's true and then it will stop. And then we have the do-while, which is just an inverted while loop, really where the check is done at the end. So it will do it at least once and then check afterwards to see if the condition is met, then continue. For each like I said, honorable mention. We will just look at a quick example of that later on. Let us look at a four-loop syntax for a for loop is four, and then open and close parentheses. And then we say int. And generally speaking, in most examples that you'll see on the Internet, you see the variable being used has no relevance using the letter i has no relevance to the court. I could've used norm, I could have used counter. All it is is a point of reference for the variable that is going to be keeping track of how many times this is going to execute. I guess is most popularly used letter because it represents the word increment. Increments means at each time. So I can be sure it for increments. But it could also be increment equal to also be a right. I'm going to proceed with I only because it's the most commonly used variable, but once again, it has no real syntactical relevance. So we define a variable, generally an integer, give it a name, and then we assign it the value of 0 at the very start. Notice you see Visual Studio is auto completing it for me, but I want us to understand each component of this code properly. So I'm not going to autocomplete on with the type and explain as I go along. So that first block defines the variable which we need as an incrementer. Notice a semicolon ends it. The second block on mobile to type represents the value that I wanted to be at when we exit the loop. So I can say I less than five or ten, whatever value I put there. If I wanted to run five times, I see I less than five. No, Why would it ruin five times even when I'm saying I less than five because I'm starting my contact 0. So if you were to do it on your fingers, I'll just read here so we can see it as clearly as possible. 012345, that is 123456 times. You see that if I start counting from 0 and then I go up to the number five, that is actually six. So that is why I say it must be less than five. So the moment it hits five means that I am exceeding my number of runs. So 010 is one, this is two, this is three, this is four, this is five. When the increments that changes the five, it's going to realize that five is no longer less than five. You see what I'm seeing? At that point I wanted to exit. So this is the exit condition for the loop. I wanted to run from 0 to four, which would be 12345 times. So if I wanted it to run ten times, it will be between 0 and i less than ten. Just so you can appreciate why we're starting at 0 and that we're seeing less than the desired number. There are different ways to write this, but generally speaking, this is the way you'll see it written. So I'm explaining it easily. Understand why it starts at 0, our white arrow instead of less than the number. Alright? No, the next block. Is our increment where all we have to say is I plus plus. So earlier we looked at the compound assignment operators. Those are accumulators, meaning you're actually adding whatever value to the origin of value and putting back in a variable. This is an incrementer which by default just sees plus one. That is almost the same as seeing, is supposed to be equal to I plus one, which if we're using our accumulator technique would be I is plus equal to one, which could also be written plus equal one equals sign, which could also be written as a plus plus. That's all we're doing. We're just increasing it by one each time. So that's why I said it's a cones are controlled. Now this could be I plus two. I'm sorry, if I wanted, it's increased by two. I would have to say I plus equals two. It would increase by two. So if you wanted to jump in twos as a counted from 0 to ten, then it would ruin 0, then two, then four, then six, then it, the moment it would be quantitative, it would jump out. So I'm just showing you the different iterations, but at a very basic level, I plus, plus, once again, I is not that important. This could be norm, this could be counter. And if I said colon transit variable here, that means that everything that I had as iodixanol relative to the word counter. That so a for loop looks in most high level languages. All right, I'm going to proceed with I. If I do console.log line inside of this, I can print that, you know, i in a loop. So I'm just sprinting the line I'm in. Expectation is that this is going to print for as many times as I have defined, which would be between 0 to ten or 00 to nine, which would be ten times whatever I put inside of this block, would be repeated for as many times as we have defined here. That means if I want to do something after the loop, I have to put it outside off that loops block. Here I can see console dot read line and we'll just print a blank line by not putting anything there, it's just going to print a blank line. And then in this line, I'm just going to say a for loop finished. I wanted to print this line ten times. And then at the end of it we're going to say a for loop is finished. So change your projects of course, and let's run. And then when it takes accuse, you see here 12345678910 times, and then the loop is finished. So that's what repetition brings, because if I wanted to print this ten times, I would have had to write the console landline ten times, which is not practical. If I wanted to increase it, I would have to go back and write it that many more times in a for-loop, I can just change this to 20. It ruined 20 times 25 to make it run 25 times, five times to make it run and fewer times, right? So just for some more contexts though, I'm going to show you what the value is. So I'm going to load the console to print the value of the counter. I wanted to say counter value colon. And then I'm just going to interpolate or I variable, which is our counter. So remember that each time this has the increase and then it's going to come back and check. Has the increased made me exceed the number? If not, then run any comments, Buck, have a exceeded a number. Null comes box. So each time it ruins it increments and checks, increments and shakes. So you're going to see that it run between the starting value of 0 and the value of four, because at five it would violate that. Let's try that. All right, so I'm running from 0 to five now you see the first row needs 0, then it went ahead. The second run is 0, I'm sorry, 1D and 2D and 3D and 4D. And the moment you'd have incremented to five, it jumped out and then went to the rest of the code. And that's pretty much all our for-loop does. Anytime you have something you want to repeat for a specific number of times, the for loop is your best bit. Alright, someone to comment this out just for now. And then we will jump down to the while loop. The while loop is going to have a slightly different syntax. Number one, I went to want to give it some form of counter. So there are number of there are a number of applications for the while loop. Let me, let me start off with the syntax. Firstly, you see awhile, then you give it a condition. So we already looked at a condition, that same kind of condition statement with less than, greater than etcetera that you would use in an if statement is the same condition you'd use inside of the while. I can see while some variable called n is less than five. Here's why I was saying I would give you the counter because there are times when you wanted to do something for a fixed number of times, you will need to truck than the number of times you have to manually go and create a variable. That's you're using a 0 counter. Then you're going to give it to a condition. It's almost like what we did between these two parts. And then we would have to do this part outside the little section of the loop. So let us go ahead. I'm going to show you the two ways. I'm going to just show you one when he meets the condition based on certain elements versus one, we have to do it in a counter controlled way. Let us say I want a console dot write line. And I wanted to see, give me a number, input number. All right, then I'm going to let n gets that value coming from the console read line. Alright. I'm asking the user for a value. I'm taking the input. And then I'm going to print at the end of it that you entered. You entered whatever number you entered, which is n, put on the dollar sign. So we get an input interpolation working. This is not a counter controlled situation. This is a situation where it's checking if n is less than five. While this condition holds true, please run the loop. Egn starts off at 0. So when it does this check, it's going to say, well, okay, I went to run this code. If n still meets the condition after printing told the screen, then I went to run it again and it will continue running it until that condition is met. So that's not a counter controlled situation. Because if I enter a 100 numbers that are all less than five, then this loop would continuously run until I enter something that is greater than five. So that's, these are condition-controlled loop. There might be times when you need it to be counter control. And at that point to doctor actually put in your manual step to increase your counter accordingly. This is where I will be increasing the colon trial accordingly. Just to make sure, of course I wouldn't be taking user input. So let me just keep it that the condition control situation and let us test. Here we're seeing inputs are number. Remember what that is going to run while in this E15 and started off at 0. And if I put you in one, it's going to say you entered one, but it checked again and sees that, okay, I'm still in a loop. Enter another number two. And then for as many numbers as I enter that are less than five, it will always keep looping and sit up. It will never let me do something that violates the condition that was coded in. The moment I enter ten, it will exit. Here. I can see while loop finished because I finally entered something that brought the condition. All right, that's pretty much it for the while loop. So the while loop would actually keep in an infinite loop. I don't know if you've heard that expression before. An infinite loop, you've probably heard it in a movie before. But this is what it is. Poorly constructed while loop can end up in an infinite loop where that loop would never stop and could even have serious consequences on your system. In the long run. You always want to make sure that you meet that condition. Or rather you write the condition in a way that it can be met to let the loop exit. This is an exit condition. Now let us look at the do-while, which I didn't mention is just an inverted version of the while loop, but it does the check at the end, right? So I'm going to take in, take our variable called n, reinitialize it to 0. And then I'm going to see, do they open up a block? Alright, so this is where the syntax is different. We say do open up the block and then we say while i, then we have the condition n is less than five. That's pretty much hold on. Let me comment this out for now. So we have a variable and just the same way we had to get the variable and get the conditioning. We have to do the same thing here, except the condition is at the end, which means that it will always do this part first, regardless of what the condition if it is METAR knots, it will do this at least once. So that's what we'll call it post check. It's checking afterwards. If we use the same code as the do-while, while, sorry, inside the do-while is going to do this. Then afterwards it's going to check if n was still less than five. So let's try it out. One. You see here, it's jumping up. It's asking me for a number. If I enter ten, which is greater than five, it's going to print and then it's going to check and see that I exceeded its. So don't do anymore. That's pretty much all there is. Say if I had set this value to ten initially, which obviously would violate this condition and an arrow. And it's still going to ask me for a value for n. Because as far as it's concerned, it needs to do this at least once. I didn't. If I change this to two, it's still going to be in the loop because now n is less than five. If I change it to four and he's going to keep on looping me until I exceed the condition. That's a that's a do-while? No, we've looked at the do-while, the while and the for loop. The for each loop would look something like this, but this is usually used for lists are collections which we're going to look at later on. But basically saying for each item or each installment or each object inside of our collection, this is what I wanted to do. So this is useful when you don't necessarily know how many times you want to do it and you don't necessarily have a condition upon which to stop. You can just use the for each to say just go through each one instead of the collection and do this, but we will look at that later on. So I'm not as I said, it was really just an honorable mention. Know, I brought up that for each loop very quickly, just know using Visual Studios, code hinting and suggestions. The thing is with these, you can actually quickly just start typing for and then press Tab twice. It will generate that block of code for you. The same thing for do, the same thing for a while. I'm pretty much it works for every block. If I said if Tab twice, it brings up that IF statement, if I say switch tap twice, it does that. So I'm showing you that after the fact because I really wanted to get the practice of typing, he told from scratch, you can appreciate it. And some of these shortcuts don't think they work as well in Visual Studio Code. So it's still good to understand all the type or the syntax regardless. Alright. At this point, I'm just going to put on that last console rather than after the do-while like I did for the while and the four. And that's it for learning about repetition statements. 15. Methods - Void: Hey guys, welcome back. In this lesson we'll be looking at methods or functions. So I'll be using both words interchangeably because they represent the same kind of construct that we have available to us in C-Sharp and many other programming languages. This point, I've already created the new project so you can hit Pause, go ahead and add the new console project, and we're calling it methods. So once you've done that weekend, continue. So we have two types of functions in most, if not all programming languages, and they are void functions and value returning functions. So avoid form shown basically complete a task and then moves along our exits. Then the value return completes a task. Yes, What's it also makes sure that's it returns a result. You can always go into on getting something back from the value returning function. The void function doesn't return anything, you just do something and moves along. In defining functions, you can end up with three parts and BSN new contexts you may not necessarily need one. You would end up with a prototype, which basically defines the function is a function header to see the type, whether it's void or value returning, and the name and parameters to be expected. All right, that's what the prototype has. Then you have the definition, which usually has the code. It contains the code block for the foam shown. What is the function doing? It's executing something. Then inside of the code, we would have the function call. This is the actual code that makes a function execute. Because our function will sit there and onto the quality won't do anything. So that's really what the function colleagues. So we have the prototype which is like a definition, which, which is kind of optional one you may not necessarily always have to do a prototype, but you always have a definition and you always have a function call. And this is the key part. Now we have been interacting with a few functions upon to know in our, in our code where we wrote Hello World and everything, our write line, that is a function. All right, So when you say console dot write line that is a function. The name of the function is right line. And I think by definition it would actually be a void function because it's not returning anything towards console dot write line. And then functions are usually characterized by the open and close parentheses. At least that's a function call. So this is what we call that function. Its definition is somewhere inside of this code file. And if we look at it, you'll see that it is actually a void function. Alright, so you see all of that comes together. So WriteLine is actually a void function as opposed to read line, which is another function in the code file, which takes parameters. Sure, but this one is actually a value returning, which is returning a string. When we talk about the type, it's either void or it has a data type. As scientists we know the data types. It can return a value of a specific datatype after it has done its function like what the red line does. Or it can be void where he just does something, doesn't send back any value. You'd be wondering, okay, so why do we need functions? Well, functions are good way to package repeatable code or code that we need to repeat. All right, so one of the foundations of programming is dry. That's a principle. When we talk about the DRY principle. It means don't repeat yourself. In a bid to not repeat yourself when you find that you have to write the same block of code to do a particular thing more than once, then you would end up creating a function. So instead of writing the four or five lines over and over and over at different parts of the application. You just put it inside of a function and the call where necessary. So that's exactly what they did with console dot write line. Console dot write line probably has a few lines of code in it. Instead of asking you to write those five lines of code every single time, they just tell you, call this function whenever you need this functionality. Let us start off with an example of a void function. What if I wanted a foam shown that basically just bringing my knee to define the function one. Once again, I need that type. In this case I'm just printing the name, so I just need void. Void is the type. And then I'm going to give it the name, print name. I didn't, I need to tell it which parameters to expect. So parameters are listed out. Inside of the parentheses. If I don't have any parameters that I'm passing in, then I don't need to put anything inside of the parentheses, but apart and disease are not optional. So by seeing void print name open-end towards it knows that this is a function and then I open and close my curly braces, which gives me the ability to start writing, watch it up. And instead of this function, let us say I wanted to keep it simple and I'm printing my name, so I'm printing Trivago Williams. That is all that I want this function to do. So imagine I had to print true or Williams multiple places. Fine, Fair enough. But then what if I wanted to print all my full name or just my first name? That means in each of those several places I would have to go and change this one line of code multiple times. Or I can know, say print name I can call this function will anywhere in my application. And then if I needed to change the way it operates, I just go to the function and change the code one, please. Repeat yourself. If I call this ten times, it doesn't matter. All it's going to do is go to the function on Meet the call. If you tried to make a function call for a function that does not exist, you of course will get an error. All right, Well, you can always have a function that exists and it's never called. Then they'll share that green line, which is just saying that it's there but it's never used. Are you sure you need it? All right. There's another principle. You ain't gonna need it, or YAGNI for short. You aren't going to need it. In this principle. Basically, say, don't write code that you don't need. If you have no purpose for this function, don't write it, doesn't have it there. Clogging up your code file because you're going to use it. All right, So let's get back to the film Shaun costs. So we have the function here. The function call will be just calling the name of the function alongside the parentheses with any parameters as needed. In this case, I have no parameters defined, so there are non required when I made that call. Alright, I don't need to plot passing any value here, just like Console.WriteLine, there are times when new console dot write line with no value being passed in. And there tends when we console that red line with a value being passed in. Alright, so this is one that t experimental. This is one that does not take parameters. We look at that in a few. So if I execute this application, it should just go right ahead and call my print name function. There we go. So this is the main code file, whatever we write in here, yes, but whatever method we put here that is only going to get this block of code once it's enough function in R, Once it's a definition of a function, only gets executed when there is a function call. So that is why we're seeing shrimp or print it out. However, if I was to remove this function call and try again, nothing would happen. Literally nothing would happen because there's nothing to happen. There is a function that was never called. There isn't a lot of code to be executed anywhere. That's his whole you call or interrupt with your function. All right, so I'm going to leave the examples of void methods are void functions here. Really and truly. Once again, it's just doing something. It's not returning a value. So if you wanted, say, a void function to do some math, like odd numbers, so you have situation where you'd want to pass in a parameter. Alright, so let us say you would want to see audition. We were talking about the potential of doing a calculator up earlier. What if you add void addition and then you wanted to add two numbers so you could put in parameters and relaunch. We'll go Allah parameter is a variable that you are defining inside of the parentheses in the function definition. And the value that is passed in will get assigned to that value in the same order that's defined. Let me do that in a code example. Let's say we have to take two numbers. I'm taking int num1, int num2. Then I want to print to the screen the sum off. Then look, oh, we can just make it look nice and professional nodes. So I went to use interpolation and put in normal one. And norm tool is, then I can just put in the math num1 plus num2. So we're not returning a value. I'm just going to call the function, give it two values, and then it's going to do the process and print the screen, but it's not returning anything to call that, No, I would say addition. And passing two values. And notice now I'm getting that into the hint, putting a value for num one side, do that and press comma. And then seeing putting a value for num tool, I do that and continue. And then D2L I would call it if we were to bolster this a bit, no antique user input for num1 and num2. And what I'm going to do is jump back over to one of our previous examples where we asked for two inputs. I believe you did that in our OK. What do you think conditional statements asked for number of oranges and number of apples? I'm just trying to work smarter, not harder, right? So enter number, I'll just keep it simple. Number one and number two. Then we are calling this number one, number two. So i'm I'm doing all of this deliberate with my naming because I'm taking variables, I'm taking values from the user. I'm starting to number one. Number two, I have defined in my function that is taking num1, num2. However, all I have to do is pass the value for number one as the first verb and devoted for normal to the second verbal. So that just goes to show that the naming here has no correlation with what is here, because I can pass in the literal values one for num 12, for num2, I can pass in my variable. That's I got from the user for number one and the variable for number two. The fact is that by the time it makes this call and goes over, whatever was first in the list goes by instead of firsts into this relative or a second in the list bands with what sick on in the list. Then the void method is going to go ahead and execute. Right now we're learning about one, making void methods to defining them and calling them, and then three, writing in our parameters. So if I run this application, yes, it's going to print for VOR because we have the print name. Sure. So it does that. They'd notice it continues with the rest of the program. So it went, it called the function, the function and said then came back and then continued node to see Enter number one. I'm just going to say ten and then enter number to 20. Then it's going to go and meet the Photoshop cough, where I addition passing into an end-to-end t. So the sum of tin and twin T is the math. Then he claimed buck realize there's nothing more and then they can fix it. That's really how functions work. So imagine that you had to write this kind of logic multiple places. You don't want to have to be writing this every single time. They asked one num1, num2, num1, num2, num1 num2. You write the method. Yes, you can prompt the user and all you do is call. If you're writing a calculator up, you can create a method per operation that would do something very similar to this. And you called Operation accordingly. 16. Methods - Value Returning: All right guys, So we're continuing our adventure into methods and hold their work. We already looked at void function, so it'll taught one that takes no parameters and we looked at another one that takes parameters. The key thing about void functions is that they just weren't operation and then they end. So if we wanted to know the end of that operation, we would simply maybe write Console.WriteLine and C and off void function. So when we press Start, it is going to the IIT being the compiler, is going to go in the order that the code was written. This is going to see that this is the definition of a method. Don't do anything in here. This is the definition of a method don't do anything in there. However, the first line of code I need to execute is a function call, which means I need to go find this function. I would have seen its definition already. Do what it says I should do. And then that's the end of this function. Then we go on to get two numbers as input. Once the user has provided those will go ahead and we see that this is another function call. It's asking for these two numbers. So it pauses, it goes, it finds that function pauses into two numbers. Those what it's supposed to do. And then that would be the end of that function call also. Alright, so that's this all void functions work. No, we're going to take a look at value returning functions. No bother returning functions do exactly what the name suggests. They return a value, something gets returned at the end. Often operation. Let's say we wanted to find the largest of three numbers. So the largest off three. So I'm going to introduce one other prompt here for a third number. So we take number one, number two, then we find out what the sum of number 12 are or is rather what does sum of them is. But we're going to have a third variable here that's going to take our third number at the end of this operation or by the time it hits this. Now we should have three numbers. Now I want to know what is the largest number. I'm going to create a method that's going to take those three numbers and return the largest one. When we talk about value returning, you have to start off with the data type. What type of value am I returning? Well, in this case, if I'm comparing three integers, then the expectation is that I went to return the largest of the three integers. So my return type is going to be an integer. If I was returning the word or a name, it would be strings. So the same way that you consider what datatype you should use for your variable is the same. We consider what data type you use for your return type from your method. I'm going to say int. And then I went to call this one largest number. And very similar naming rules apply with methods, except we tend to use the pasco case for methods as opposed to CamelCase. So remember plus Co case means that you capitalize the first letter as well as every other first off the other words in that block of text, that's your typing. Alright? So int largest number. Then I'm going to tell it that it needs to take three parameters here, Visual Studio suggesting that IT num1, num2, both int button went to introduce a third one, int num three, because I wanted to take three numbers and as many numbers as you need you list the most of course. No, you'll see that I've already line here. I need to see in that not all code paths return a value. So I like explaining what these different errors mean because sometimes it's not very obvious, right here, ETC. And that we have a method that it has seen is a value returning, but it doesn't see anything being returned. All right, so that means we need a keyword and that keyword is returned. After return, we need to stay at what we're returning. So here I'm just going to show you if I say return 0, it is satisfied because 0 is an integer value, an integer value, and it has the return statement for the integer. So it's expecting me to return an integer. I have this statement seeing I'm returning an integer. If I put you in a string like my name, then I would get an error because this is not an integer. So it's good to see you cannot implicitly convert type string into int y. This is a string, but it's expecting an integer to be returned. Those are little things that you have to look out for when dealing with value returning functions. So let's just go through a quick exercise here. I'm going to show you another thing called nesting, which is where we have one control structure inside of another. So R1 type off construct inside of another meaning. Here we have a method, but I'm going to put an if statement because the only way to know what the largest number here is is to use an if statement or some form of decision logic. I went to start off by seeing that the largest number is equal to num one. This is just an assumption because one of them must be the largest. So I'm going to assume that no one is the largest, but then I need to test if the largest number is actually greater than num two, num three, then if either one of these is greater than, that will be the new largest number. So I went to say, if just the same way I said it, if largest, let us see if largest is less than num2, that obviously largest needs to be equal to m2 because the largest number cannot be less than name2. If it is less than, then I need to reassign. Know num2 assumes the role of largest number. Then I can say if again, if the largest number is less than num three, then Visual Studio is going to assist me again and let me know that the coordinator at is that the largest number is not equal to num three. Notice I have two statements. I didn't use if else, if or whatever because I needed to do this comparison. And then these comparison, if I did an if else, the only way it would go to this comparison is if this one wasn't true, you'll want to be very careful and very deliberate with those kinds of things. If else means that I'm going to do either or. So if this one is true, then I don't need to look at this because this one was true. However, if I do completely different and individual if statements, it will check this. If it is true, then it will go into the body. Then it will check this. And if it is true, it will go into the body. So this is saying that if normal one starts off as five, and then it tests to see if the dot five, which is the largest, that's the value five, is less than num2. And let us say num2 was 105 is no less than 105 is less than ten, that is true. Then no largest gets the value of ten. Then it will move on to say, check if ten is less than, let's say three. If it is not less than three, then this will not get executed as this was not true. Then we need to return. If you said largest, then you are definitely correct. We need to return that value. So this is returning an integer which is deemed to be the largest number. So the method you name it according to what you know it's supposed to do. Yes. Well, you always have to make sure that whatever logic you're outlining in there matches the intended operation and whatever value is returned matches the expected icon. So you can imagine that you wrote a method to calculate somebody's tax and then you've got the calculation bit of it wrong. So every time you call that calculate tax method, it was returning the wrong value and you are taking too much tax from this person, that would not be nice. So it's always good to understand what logic here putting in relative to the operation at hand. And yes, I can sit here and show you examples where you have to practice. That is how you get better at this. So you get better at making these decisions. We have determined what the largest number is and then we return it null. I can do a function call for largest number. After getting all three numbers. I cannot just say largest number and then pass in number one. Number two, number three. All right? No, when I pass this in, what happens? I'm just going to call this method. It returns largest. And then what happens? We know that without a Console.WriteLine, nothing is getting printed to the screen though the console read line, nothing is being taken from the screen as it's tons when it hits this method, It's good to come up periods, go into the numbers shores going to do this. It is going to return largest water wheel. We have to bolster this a little bit more. I have to actually put this inside of a variable. So I can know C creates a variable called, in this case result, and it will be equal to the results of this function call. Just the same way we've been doing the same thing here when we ask for input. We say console dot read line, or we said String name is equal to console dot read line. It's calling a method, and then it is assigning it to this side. In the case of software, we have to do conversion, convert to in 32, that is a value returning function. All it's doing is returning an integer, right? Same thing for it to convert the char and to bool, etc. It's just returning whatever datatype it said it will return. That is why the assignment or the variability it's being assigned to is very important. So int number two is equal to convert in 32, That's method call one. But in where passing in another method here that will. Give us the value that will be converted and then our science. So it's the same thing here except where to want to write your own method. This time, I'm seeing creates a variable of type integer called result and assigned to it whatever is returned from this method called largest number, which is returning an integer. Alright? So when we pass in those three numbers, come up, meet the comparison, return whichever one is the largest. And then when we return, that gets stored inside result. So no, I can see that the largest number is. I'll just use interpolation here and see results. Interpolation means I put the dollar sign at the front of the stream. There we go. Alright, so nobody's going to print the largest number is result. No. I'm going to show you another way you could have done this. To use fewer lines. You could actually just print that. Alright, let us see. We could say console dot, write line. This block of string is, and then put in that function call inside of the interpolated section. That means it will go and meet the function call. The value gets returned and that value is what will be printed inside of that section. So I'm just showing you, I'm always going to show you your options. You could do it in two lines like this, or you could do it in one line like this. I tend to prefer using two lines because that form MY increases the readability. I can clearly see that this is a variable. This is how it's being set. And then this is always being used as opposed to a longer bit of text where I have to put on good lenses to see that this is a function called happening inside of an interpolated string, inside of this, inside of that, why it was still work. You also have to consider the readability of your code because you might be writing it for yourself. Nobody looks cool. Maybe take a break and come back and you'd be like, what, what did I write here? Why did I write it like this? Or somebody else may have to look at your code. And they weren't thinking the way you were thinking when you wrote the code. So it's hard for them to catch on. So you always have to consider those possibilities when you are writing your code. So sometimes things could be done in one line, but I split them all just to see him because it makes it easier to digest and read. All right, so let us test this out. I'm going to run without debugging. Then let us put in over three numbers. So I went to put in 1056 and it's going to say the largest number is ten. Hold it no. Because largest norm. Largest got the number ten initially, right? That was my normal one. Then it said, if ten is less than five, which it is not. So it skipped over that. And he said, if ten is less than six, I think up within it is not. So it skipped over that. So it returned ten and then stored tin instead of results, which is what got printed to the screen. That's his whole value returning methods work. 17. String Manipulation Functions: All right guys, So we're kind of coming off the beaten path of exploring the B6 of C-sharp development and going into a few more advanced concepts. And one of those is a string manipulations with a string on D8 time manipulations because those two datatypes, as seamless deme look, can cause a lot of problems if not handled properly. We're going to be looking at some of the ways that we can manipulate strings. We've been doing it for us to some extent upon to know, but we'll be looking at some others. And we'll also take a look at dy dt time values and hold those can be manipulated as well. Let us start off quickly. We know how to print, so we know how to print the string. I should say print to screen here, sorry, that is console dot write line. If I'm to print one thing that I just see, the one variable, in this case, Visual Studio is actually helping me with concatenation. So that's actually the code for the second one. If I just wanted to print first theme that we know what we just say, console.log line, please in the string or the variable, or it is a static stream that we pass in. Whichever one works once it's a string variable, well, frankly, it can handle almost every variables as far as we've seen, all the simple primitive types at least. So those are your options to Print Screen. Now when it comes to concatenation, we know that we can use our plus sign. So here I'm seeing Console.WriteLine, the value that is in firstName, space in-between, and then another variable. We also know that we, if we wanted a static string plus the variable, we would see my full name is. And then we would be able to concatenates the variable. And then as many other variables as we would need, we just flows with the empty space. So the relevance of the species that prints, it's going to print exactly what it sees. Its printing my space, full space, namespace is space, then lastName, then space again, then first name. So that's the importance of having that little space in there. Alright? No, Although way as we have looked at doing concatenation would be using interpolation where instead of using the plus signs, we can use our curly braces. We just sprint one block of string. But then of course you notice that I using variables here, but they are still orange. I need the dollar sign at the front. I'm gonna take note that it's an interpolated string so that it will know that anyway sees the curly braces, that should be a verb in there. All right, so this is another way because now it's sprinting my space. Full name space is then the last name space, the FirstName, lastname, firstname. Usually you'd have like a comma, so it'd be williams coma for VOR. See that even though I am typing in-between the two variables here and the interpolated string. It's going to see it as one being contiguous block, just going to super impose the variables that it knows it needs, need to be there. Generally speaking, these are the most common ones that you'll find in water and C-sharp. But then the alternative, of course, like we had looked at was using placeholders. So we're not using any interpolation. Instead we're using 12 and as many other police folders as needed. And then we just put in the variables that match in that order. So first name, then last name, last name here, would much please holder 0, firstname much as placeholder one. Those are ways that we can handle concatenation in strings. No, there are times when you may want to know a whole long is how many letters are in the first theme, for instance, if I wanted to do that, I would want to find the length of the string. So I could say int, let's say length is equal to. And then I can call the variable. And then look at that Visual Studio is contextually autofill in that formula. So it's going to say, get me the variable, look at the value in it and telling me the length. My name has seven letters in it, this would just return seven. This is a property on that string called length. When we get into classes and objects, Yolanda, similar time you buy a property. So don't worry about that. The use of that keyword just yet. That's it. So you would see the length of a string. If you wanted to print that total tough course, you would say something like console dot write line I used just say length or let me just make it a bit clearer. Someone to use the oldest style all the way off concatenation. This would be seeing your name is. Okay. Let me make this into a whole sentence. So this would be interpolated. Let me make it into polluted. Your name is, and I can put in that many letters long. Close the stream, and that's it. So it's printing out a whole sentence with a variable smack dab in the middle of a literal string. Now, let us move on to something else. What if we wanted to replace letters? So let us say I wanted a new name or I wanted to see what my name would look like. If I replaced all of the t's with the letter key. I can see a first name, dots. Then if you do the dot, you see a number of what we'll call methods. We looked at methods already. Just like we can say, console dot, write line is our method. You can actually on any string variable c, variable dot, and then you'll see a bunch of methods. Some of them are useful, some are not. Just to see him week and have this property. So if I say Replace, then you will actually see that there is a method they're called her please. And it wants two things. It wants the old char or character, wants a new character. I could see the character t. I remember characters use single quotation marks and only one value can go instead of a single quotation mark. Alright? So that's his character. And I want to replace it with a new character of k. This is going to automatically evaluate this string and go through and find all the T's and replace them with K. Alright, I went to pause here and do some testing. So let us change over our our project is through manipulation. I hope you had already done that. I'm sorry, I didn't points he told earlier but create your project clustering manipulation. Or maybe you already created it with a different name. That's not really the big points. Just make sure you're running in a new method, in a new project rather. Then let us run. So here are the printout. So we have traversed string being printed. There it is. I know we have all of the different ways that we did darkened cutting concatenations and it will have your name is seven letters long. And then we did the replace with new name what I did not do a sprint the end results someone to see your new name is, and then I'm going to see new name. So that's Australia. That again, right. So here we have your new name is Chris. Oh, I don't I don't like the sound of that one. Right. But now you see what it looks like. So even if I wanted to remove litter, let us see the eye. So my name is quite unique because it's really trivial. What's an eyes in there? And it's Greek and it means reservoir of strength. Both a lot of people, when they call them by name, they just call me trouble. I don't really make a big deal out of it, but that's fine. Let us say I said new name, one is firstName, replace the letter I, the character i with nothing. I could see it with a space. Because really and truly a character can't be empty like that. That's why you're getting that green, that red line. You can't have an empty literal character. And there's no car dot empty like older is a stream dot mt, is there? No, there is not turret. So let us just see, I'm going to replace it with a space, so a species, actually a character. Alright, and then I went to see your new name is new name one. So let us see what that would bring up. There it is. So no, it has that space where that I was told that replace operation works. Alright, so let us move along. The next one would be to append to other string variable really and truly that would look just like this concatenation here or any one of these. Because we see that you can actually just combine them, right? So I could actually just see var, sorry, string listening gets so var, string full name is equal to one variable combined with another variable. And that's it. Or if I just wanted to combine them without anything in-between yourself to C plus, alright, so once you put a plus sign between a string or between two strings, would that air literal strings are string variables or a verb that under literal string, however, the combination, you just use that plus sign. So that wouldn't give me my full name, which I can print. Your full name, is an employee until the full name there. Now the next option would be to split the stream. And you can see here that I started writing the code would have an error. And the error is saying that it cannot implicitly convert type string with those boxes, with those are two square brackets tool regular strings. So in other words, this would actually give me a collection of strings. So here I'm seeing the full name. That'll be traversed space Williams and split it. Wherever there is a v. As many visas may appear in the one block of string, it's going to split it accordingly. So if there are three V's, then he's going to split it to the left of one of the V's, to the riots off that V and into the write-off the next V, That's pretty much what it's going to do. So in Trevarthen Williams, There's one VC would end up with that side. And this side as two strings or two blocks of string. So I can't be storing two blocks of string in one string, which is why I said it needs the square brackets, which means we're not quite ready for areas yet. We're not quite ready. We're going to explore it in more detail. But I went to show you what the outcome of this operation is regardless, the best way to iterate through an array is to use a for-loop. So usually say like four. And then we already went through a for loop. For int i, which is my counter, is equal to 0. I is less than the length, meaning how many times do you want it to go through? And then I plus, plus. In this case, I don't know how many blocks of string I'm going to get. I don't really know because I don't know what the full name is going to be. The full name could have been user input where the person Internet stream with no v's in it. So there's nothing to split equal to 053 V's in it. So R5, I don't know. For the length variable, I wouldn't want to put ten because then I went to go ten times and maybe only needed to do two times. And then that is actually going to cause a problem. Again, I'm not getting too much into detail with Ari's just yet. However, an easy way to navigate this would be to take this array of strings c. Instead of giving us specific number, I went to see the IRI dot length, whatever length, whatever number of elements are blocked. So Stream come out of that operation will get stored here. And each one is going to call Windows one. Each block is going to be one block inside of this collection of strings. I'm saying get me the number of blocks in the collection of strings, and that's the number of times I want you to loop. We're going to go more detailed into that later on, so don't worry about it. But right now I just wanted to show you the console right line. All I would have to do is say, give me the split name value per subscript that is in I. Right? I'm just going to print that out. And then when I looked at it in debug mode, I'm going to see tray and then, or William, that's really printing out here because that v would be the splitting points. So what's the lift of the V? What is to the right of the v? More, V's more splits. So that's what I said. We don't know how many splits we would get, which is why we tried to keep it dynamic. Once again, we'll be looking at that. The Concept of Irony is later on. Lets us move on to the string comparisons. A string comparison me occur when you want to compare something that's a user entered to a potential option, or you want to compare two values to variables. There are number of reasons you need to compare strings. So a very common comparison that you may end up doing is checking if something is empty or default. Because like I said from the very beginning when I defined the string, Let's say variable, test variable. Remember, I defined the string and I didn't give you the value at this point, it is what you call null. All right? That's another point. You may have given it. This. It's not null, but it doesn't have a value. So it's not, no, it's just empty. Just isn't the same way. That will be the same thing as seeing string dot empty. All right, so these two would actually equate to the same theme. Let me just put that as a comment there to show that that means stream dot empty. All right? And in other, in some situations you don't know if the user actually put in something valid or so-and-so you have to check if it is true, if the null, sorry, if the string is null or if it is empty. There's a built-in method where when you type the data type string and then you see a full stop, you actually get a bunch of methods also looked at that. You have is molar empty and you have Ismail, our whitespace. Whitespace would be more like this, where you just put a space in there. There's nothing there. I wanted to say null string. That's on those string. This is an empty. String, then this white space, straight, just so we're clear what each one represents. Instead, I'll see you in test variable. You can see is null or empty, which will either say yes or no. That's going to return a Boolean value returning function that's returning true. It is not empty or null, it is not knowledge is not empty. So they need parsing the string. So you could see no string here if it is null or empty. And that's where you would say, well, I have an ISI here. I cannot proceed. And actually, when you look at that, so in C-Sharp, in later versions of C Sharp, it's actually preventing me from using this without first assigning a value c. I would have to explicitly see here that it is null in order for it to proceed, that you could just assign it as null, not assigning it. The compiler is not going to take any guesses and say, Oh, it's no, it's not limited to that. So you have to explicitly say it's not. Like I was saying, you could actually, if it is smaller, empty and it shouldn't be null, you could take oxygen. Those are considerations that you have to meet. Another easy you'd probably want to. Let me just split in our console right here. So they now see string is null, one citizen alert empty. Then we will just see it is not. The reason you would want to compare strings is if you wanted to compare two of them. So the same kind of equivalence that you would probably apply to a math operation can apply to two variables. So I could see if firstName is equivalent to lastName. Then take some option. Names are equal. That's something you could do. You could also see if they are not equal. I'm not equal would be exclamation equals sign, not equal to c. Names are not equal. So those are other things that you would want to do another week and compare two strings is to see if then string has a dot-com peer method on it. Then he can policy and the strings that you want to compare. So here it's showing you that you have a few options. You have nine overloads. We be looking at overloads in a few bullets. I can pass in a string number one and number two, which is last name. And then it's going to return, if they are, sorry, actually this is returning an integer. So let me try that again. So I would actually say int comparison results is equal to the string computer. That's integer. Then it saying that a value that's less than 0 shows that are actually a valid, that is not 0, shows that they are different. Pretty much results or whatever variable value you get from this comparison. If it is equivalent to 0, then that goes to show the names are equal and I can just do an else. Names are not equal. So this is another way that you can check that there are several ways I cannot exhaust all of the methods here and I can assure you as you go along in your professional or even recreational pursuits, you're going to find different ways, different needs for string comparisons that cannot be covered in a single course. So it's audible practice and exposure. Next, let us look at how we convert values. So strings. Typically speaking, whenever you want something to be a string, you would give the variable the datatype. Um, let's see, convert, converted value, converted string, it's called a converted string, is equal to string dot empty. I'm just initialize it to stream dot mt. Know if I have a number that I want as a string. This number could be a specific number that I wanted to type like this. Or it could be in a variable. Int number is equal to this value. And I wanted that value to be stored inside of this variable. I cannot just say convert this string is equal to number. We've exhausted that. We can't just take some numerals on police inside of a string. It does a word that we, instead we have to convert it the same. We will have to convert tool in 32 from strings and see what we have to convert toString from any other datatype. C-sharp makes this very easy because there is a method on every variable that you will ever interacted with called string. It's so cool that even the very numeral that you would've typed up, you could see a dot to string onto the end of it. So just by typing this numeral I and then putting dots. So string, you would actually convert it to string for you. Any variable, whether it's a Boolean, a number, a double, whatever it is, you can also convert it to a string. But just remember that when it is a string, the plus sign is going to work entirely different from how it would've worked if it was a number, right? So remember that plus signs when we're dealing with string concatenation. Whereas plus signs when you're dealing with math, will actually do actual math and add the numbers. So be very careful and cognizant of that. But for norm went to pause with string manipulations. You can go through, you can experiment, see what other methods are there. Other cool ones like you can see upper and lower, you can do joins. You can create. If you just write string1, press dots, you can skip through and see the other methods available to you on the variable itself. You can actually let us say fullname and I see it. I can actually see two upper if I wanted everything to be uppercase. I could actually say to lower, if I wanted everything to be lower keys. There are number of methods that are there to help you manipulate a string without too much work involved. So I went to leave you to experiment and explore. 18. DateTime Manipulation Functions: All right guys, welcome back for our own tools. So Gondwana was all about strings. I intended to do both strings MD time, but you'll see that the activities to cross over into another lesson. So that's fine. We can catch up here. So I haven't created the project has yet. Go ahead and do that. You can follow along with me or hit pause and do it on your own. So of course you have to go create our new project. We're going to go with date time manipulations. Then we hit Create. So now that we have our new project, let us see what tasks are there for data manipulation. Here are the tasks that we're going to go through. Much like string manipulation and data manipulation is very deep, very extensive, and very situational. So there's certain things you mean never end up doing in the foreseeable future. And there are certain things that you may want to do that I'm not going to necessarily showy in this time-space. Let's just work through it. I'm just going to vary in some of these things. We can additional time. Sorry. We can just work through it and see how best we can on the sun. Firstly, a datetime represents a datatype in C-Sharp and it's sounds like primitive datatype. So when we talk about primitive datatypes, we were talking about int double stream, the very basic date, time, or a more complex data-type would be a combination of different datatypes that extends the functionality a bit more. When we talk about dates and time, talking on boats, a datatype literally called the time. Then we give it a name. So I went to call it. Then usually you want to initialize this. And we initialize this is by saying I knew the time, open and close parentheses. So this is the way you would initialize a datetime object, not variable, what object? We're going into the realm of classes. So notice that it is kind of that teal cyan. I'm not sure what color that is, what it's the same color that console is. So Console is a class. Datetime is also a class, and we'll do string is blue, int char, all of those are blue, they're not the same color. Those are not classes. That's it. So you initialize an empty date time. Now let us look at how you would create one. So let us say I wanted to create my date of birth. I could see a date, time, or date of birth is equal to a new datetime object. And then I can actually pass in values that I would like. So if you look through, you'll see that you have a number of options. Here's the one I want. I can pass in an integer year, an integer month, integer d, the year I was born, Let's say I was born 1980. The month let's say I was born December. That's the 12th, right? And then today Let's was born on the 35th. So of course there's no 35th. But it's not going to give me an error here until I try to run it and it gives me a problem. So I went to do a console dot write line. I'm trying to print out date of birth and notice I can just pass it into the right line because it does accept more complex objects also have the primitive types that we have been working with. My D OB is I'll just use my plus sign here. If I tried to run this, let me change it to date manipulations and try to execute. Then, wow, we're seeing that we have these exceptions. An exception is an error that usually occurs in our program and kills the program pretty much. If you're using Google Chrome or even Visual Studio and you get one of those areas, even Windows. And you have that blue screen of death, all it's doing is hitting an exception. An exception is one of those irreversible arrows that assist him did not account for. In this case, it is saying that these are not representable bedtime the values that I presented. So yes, the area is fine, the moment is fine, but this is not fine. So if I put it to the 31st and try again, then I should get that print adults. So notice just by passing in that datetime object equals able to print out the 12th to the 31st and 1980. That's what's my date of birth. All right. Nice and simple. Now, what if I wanted the current timestamp so I can see a dead time. Let's call it no. I wanted to know what is the time, right? No. Then literally I can see a date, time, dots null that will go to your system, gets the timestamp as at the moment the code was executed. And then that will be stored inside of this object called null. So the time now is is, and then I'm going to just print no, Let me try that one. As at the moment that code executed, the time was the date, was that the time was that I'm using are my time on my system. It's going to reflect what the system time is, an even the layout of the date format. All of that is affected by the system settings you have when the school is executed. So if you're on British Standards or four months, it may look slightly differently in terms of Using De Montfort instead of month, day, year. And if you're not using armed time, then your time We'll different. Those are things to be mindful off when it comes to printing out your date-time. Know what if we wanted to create the DateTime from a string. So to do that, it means that I would've had that kind of string representation that was just printed out. And I'm using that to engineer. I did time value. So I can see datetime, time and I'll say did from string is equal to. I can do a datetime parse. Just like strings. There are number of methods involved. But it wants the string. What is, what is the stream that it's supposed apart? So what if I said one slash 31 slash 2221? That should be January 31st, 2021. That sees what I want to parts of other parameters that you would add like parameters to let it know that culture in full. Let me see if I remember how to type this in variant culture. So there are different parameters you put in to let it know. Don't be specific to the culture. Here. I just added that using statement for this one. It's actually a static class just like console or LN. So I'm saying culture in full, in very uncultured. So it says the culture is, it's an independent, it's culture independent because like I said, the format sometimes will differ based on your culture. So just by doing that, we can make it independence. No, I did something and I didn't explain it while typing all its culture in full. Udot seen the red line, which means that I'm trying to use a method that's from a library that is not included. Remember we have to add are using statements whenever we want to use methods from, from libraries that are not already included. So I had to do Control dots. And the suggestion was I can add the using statement. So by doing that, it automatically went ahead and added it for me. I know I can access that method. I'm just showing you once again different variables. I'll see the time. The deed from string is, I'll just print out the ID from string. Let's take a look at that one. All right, so doing that really and truly it took it, it parsed it into daytime and then it really just re-post it back into a string. All right, so that's just an example of how you can convert from the actual string into that actual datetime. Datetime is an actual datatype that you have to be mindful of when you're especially dealing with a database. Because you'd be accepting string input from your users if they were to enter it in through the console, we'll just store it into a database. You would have to have it as a date time. So that is one of the other reasons you'd want to be careful. Now what if we wanted to see what is an hour from the current time, right? So I already know. What if I wanted to add an hour to see what time it would be? I can always say no dots. You have options to add hours. You can IDs, you can add milliseconds, minutes, months. He can add almost any construct of time. Existing datetime variable. So I can see no odd OA. So if I just wanted to see one hour from now is one hour from null is, then I can just see no dot add hours prune told No. It's already gotten up top here. He knows what time it is, no. And then it's going to calculate, well, what is an hour from now? I could see one d from NOW is no dot add days. Once again, exploration. So let's see what that looks like. When we get that, we see that null is 1241900 hours. One hour from node would be 20. $100.1 day from now will be the 25th with the same timestamp as it was. No. Alright, so all of those calculations are brought to us courtesy of these methods. Now the next one in the lineup is dead time from ticks. But I think I went to invert it and we'll just say ticks from the time I take. Or ticks basically represents the number of clock ticks since time was being, let's say calculated as at this moment, if I say console dots, right. A time numeral, pretty much if you were to give a numeral value at the time, he would be in the form of Dijkstra is I could say no dot ticks. It gets the number of things that represent the date and time off. This instance, this moment, there had been this many ticks on o'clock since we started calculating time. That's pretty much what ticks would be. Before I test that takes, let's just jump into data and time only. So dates only and time only our brand new constructs and C-sharp tin where there are times when you wouldn't necessarily want the time on it. Because here d itself, birth wouldn't necessarily about time. Dates of birth is just the year, the month. The right. Of course, you could add on the seconds, minutes, and hours if you wanted to. But we don't necessarily want to do that because you see here if I keep on typing, you will start seeing he didn't hour into minutes and seconds. So that's when you talk about date and time. That would actually be 1980s, the 12th of the 31st of December, 1988, hours one minute and 35 seconds. There tends to be that precise. All right. I could actually see a date only is equal to date of birth. Let's say D, it's only off birth. Just so we can how some distinguishing characteristics, date of birth. And then I will take an existing datetime object, that date of birth. And C, I want the D only. I see indeed, it would bring me back just that actually. Actually no, date only dots from date-time. There we go. I apologize. This is a fairly new construct, so forgive me. All right. So dot ds would really just give you about the dates, right? Let me, let me put that one up here. Would actually just chop off the zeros that would have been seen after the whole datetime here. All right. So that should give me about just the deed. Then the date only construct is going to just give me back d It doesn't care about at the time. But if I have a date time, I can say give me the date only from date time and give you that datetime value. In a similar manner, I can see time only. Let me get most spilling right at time only. And I'm just going to say time. Time only is equal to, and I can do that time only from the time. Let's try it out with no cause I know that it will have an actual time attached to it given that it's a timestamp. So let us try all of those together. Here. I'm seeing that even though I said it's still going to give me back the deet still getting above the time component to the right. What we didn't do a sprint these, so let me just add the sprint only. Let me just add these in quickly. And that will be d dt of birth. And then mix this one up. So let me fix this a bit. We're going to say time only is time only. After putting in the console. Let's try that again. No. Once again, even though I said dates of birth, give me the full datetime and then give me the datetime dot d t. You can see that the time stamps are still trying to be added. Went through the Timestamp, went through adding an hour, and these are the ticks. So as at this moment, this whatever that number is, if you want to try and call it, you can let me know what that value is, what that is the number of ticks that I've gone through since we started calculating time. Then the date only here represents only the date. So this is literally the date of birth, not the date, time of birth. All right. And then if I wanted a time only, it is the time so that it took the timestamp and give me just the time, not the date and the time. So those are some ways that you can manipulate dates and times d or advantage. I can assure you once you're putting on functionality that has to deal with Dietz and timestamps and particular things at particular points in time, you will definitely have to become familiar with some of these functions. Once again, I cannot see potentially every single one of them. There are things that you have to explore, how to experiment with. They're also things like returning the year. So what if I wanted to know which day I was born on? I could say date of birth dot d off week. So that will give me back if it's 1234567, day of the week, he will give them the time off D it will give me the day of the year, right? So there are 365 or 366 days in the year. Which day of the year was that? If I say give me about just the D, it's the integer of the D, right? So day off, day is different from the off week because D is obvious. We know it's the 31st, however, the day of the week that was the 31st in 19981980, we don't necessarily know that d of weak is another construct. You have other things like I just added them. So the off week, day of your time off the tick, the number of ticks. When I was born, and the kind, right? So if I just one more execution just to see what gets printed out for all of those values relative to date of birth. You see that? I was born. I know it's there. It was the 366th day of the year, so that was a leap year. So you can bear that in mind when trying to calculate leap years. You can see the time off the, well, I didn't specify a time, so time of day would actually give me something similar to the time only. This was a number of ticks, right? So if I did some math and I said This number of ticks, this number of ticks, I would actually get the number of ticks between the two times NO, and the date of birth. The kind here is on specified. So kind of would actually refer to whether it's UTC or ESD or some local time, pretty much so I didn't make any any specific locations as to watch timestamp or time zone. This was so kind is unspecified. So those are some ideas when he comes to the manipulation. 19. Exception Handling: Hey guys, welcome back. In this lesson we're going to be looking at exception handling. We looked at exception handling earlier. Are we encountered an exception rather earlier when we were looking at our datetime objects. And if you remember, when we create a one-off those objects, we put in an invalid value. And then the program gave us an error. It gave us a block of text that I'm sure if I didn't read it and explain it to you, it wouldn't have made more sense. That's generally what an exception is. An exception is an, a fatal error that would occur in your program. Usually gives a very nasty error. And it's not necessarily something that you would want your users to see. So just rock back in your memories and think about every time you see Google Chrome crashing with a message that makes no sense. Or that blue screen of death on you're on Windows or some error that you encounter in an application where that application and shows you an error. And then when you try to navigate away, the application might crash. There are also times when that application does not crash, but it goes into more of an error state allowing you to continue your operation. No, that is what we call exception handling. The error itself is an exception. Then the way it is dealt with is what we call the handling. In C-Sharp and most other languages, exception handling is done through what we'll call a try-catch block. A try or the trip portion of the try-catch is basically going to try the operation. All right, so it's good to attempt to complete something, complete a task. They catch section off that whole block, is going to catch any fatal error or exception that may occur while trying the operation. Then usually you will see, or sometimes you'll see another block called Finally, meaning whether, whether the trie or the, the catch was successful. Do this at the end of trying, maybe catching, do this. If you try it and do caught, then still do this. That's pretty much what that find that it does. And then another keyword that you usually see in exception handling is true, which means the program execution with the error. All right, we're going to be going through a little exercise here where we're going to explore under what circumstances there might be errors. Watts we can do when there are errors and why we would want to do those things, right? So I went to start off with a very simple application. I'm just going to reuse one of these operations that we have before. This wouldn't and borrowed some code from one of our previous examples. You can just hit Pause and replicate that, but I'm just saying enter first number, storing it in num 1 second numbers during genome to hit pause replicated that. No, generally speaking, you would want to do some form of operation here. You'd want to say, let's, for instance, say the quotient of num1 and num2 will usually be num1 divided by num2. Simple math, num one divided by num2. Then you'd want to write that the quotient is whatever that value is, results is. Then I'm just going to concatenate that. Alright? So that is a typical math example. I went to. Firstly, run this operation. And I already created the project. Of course, as you can see, I call this one exception handling. Exception handling. Let us run so it into the first number that's ten divided by one. The result is ten. Okay, straightforward. Let's try again. If I do the same thing with 100. My look at this. In Visual Studio. I am getting this yellow arrow. Nobody went through debugging already. We know that this yellow arrow usually indicates which line you're at, especially after you've put in our breakpoint upon to know, I'm sure that you haven't encoded this yellow arrow popping up off its own volition. Then furthermore, you wouldn't have seen this red X with the message excepts on unhandled. So here it's saying that we have a System.out divide by 0, exception, attempted to divide by 0. So there's certain things that cannot stop dividing by 0 is one of them. And the system, system being your computer, being computers in general, cannot handle an operation where you are asking it to divide another number by 0. So this is what causes an exception. And then this kind of exception is what would crash your program because you see it just stopped running. And now I'm getting this nasty error in the console saying unhandled exception, then this means really, I mean, it probably means nothing to you as a beginner. And that's fine. I've seen enough of these over my career to understand what it is, seeing. What the point is that you wouldn't want to display this block of text or anything here to our user because that makes no sense to the user. So imagine how you feel when you see Google Chrome or whichever application I keep on using Chrome because Sita allows groom what they handle it well, but they do sometimes show some obscure errors. I think they've been doing much better with that in more recent times. But sometimes you see those obscure error. So those are the exceptions happening inside of the application. And that is why applications tend to say, do you want to do that feedback program where when they encounter an exception, you actually send the message back to them. So they get this kind of message in their email saying this happened to a user, which is why you get updates. No application is perfect. They all have arrows somewhere somehow. That is why you keep on getting updates because then they would go into code and fix it. So let us fix this one. This is an exception that we didn't account for. Let us fix it. So we can wrap that inside of a try-catch. Like I said, the trie represents the operation you're attempting. I can say try and just by writing trend pressing Tab twice, it will generate this entire try-catch block for me, this block is what we would try. I mean, couldn't be as many lines as you need is the operation that you're trained. Because sometimes you have 235 steps in an operation and any one of those steps could throw an exception. So then when we throw an exception, for instance, or division operation would be what we're trying. If this does throw an exception, then we have this catch block. Notice it says catch exception. Exception is the general datatype used to identify when an error has occurred. They're all just exceptions even though you'll have specific ones. They're all at the base of exceptions. You catch the exception. And then you can actually store this exception instead of a variable or an object. So we can give it an object II or III eggs or call it exception with all lowercase I went to leave it as EX law. So basically we're saying try this operation, catch any exception or error and stored the details offset exception or error inside of this variable called EAX. Then you will notice that you also have this keyword called throw. Throwable is what actually kills the program. So if I was to remove throw, you would actually continue to execute. So when we try and it catches the exception, if I don't through. So here's where I would probably send an email it or write it to a log somewhere where there yet. But I'm just giving you the ideas because we use applications every day. These are things that we see anything there. But I'm just showing you that it's really coming down to these little bits of code. Right here is where that application will show you the dialog box and say, hey, you know, we sought out to you, encountered an error. Would you like to send a report to our developers? You say yes, then what they did catch showing you the dialogue. If you say yes, then send off the error that was caught inside of this object. That's all that's happening. Then at the end of the operation would print or whether we can't print because this variable exists within this scope. This is a good place to talk about scope. If you define a variable in-between two curly braces, that variable only lives for as long as when it hits that line and that curly brace ends. That soak in a little. So that is why I cannot print quotient outside of the try catch because this variable only exists inside of this try block. So I can do anything I want to caution inside of here. Like I can print it inside of the tray. Once I cannot interact with it wants to try is done. So that's why I cannot print outside off the tray lighthouse trying to do initially. Those are things to be mindful off. Let us continue now, if I say throw, then would end up with the same kind of situation where it just ended the execution altogether. You don't necessarily want to throw, unless you are absolutely sure that that is your desired effect. If you do want to kill the program, when that particular areas in concert, then you want to throw. So let us see that dividing by 0 is not the type of error you want to throw on. However, if you catch any other kind of exception and then you do want to throw, you want different reactions to different types of exceptions. Well, you can actually have multiple catches. You can catch a specific one, let's say divided by 0 exception. And then you can decide when it is a divide by 0 exception. I want to see illegal operation. Just say illegal operation. And then I could actually puts this exception message inside its own object also. So let's call it EX. So if you catch this exception, I'm storing it didn't set off EAX within this catch block. And I'm going to print the message that came with exceptions so I can see EX dots. Then we see message. When I do that for semicolon at the end of it, I'll catch that kind of exception. Otherwise, any other kind of exception through maybe send an e-mail to the development team and throw kill the program because I'm not prepared to continue after that. All right? And then I'm going to just say finally. Then in the finally block we can just Console.WriteLine. I'll just say this is the finally block. So that's bad. Let's try that again. This is the finally block. There we go. So what we wanted to do at the end of this is whether we were successful or we call it the division by 0. We want to save this as the finally block. Or let's just say this is the end of the program. Off the program. Let us try it out. One exception handling, run it. And then I'm going to do a proper division. So I'm going to do 105 and then I get two. And you see this is the end of program. So it tried, caught no exceptions and then did the finally. All right, so let us try that one more time. And this time I'm going to try and get that divide by 0 exception. We're going to see that it was still jumped down to the finally and continue with the exception. So if I say ten divided by 0, it will say illegal operation colon. That's my static string that I typed. All right. And then the EX dot message would be the attempted to divide by 0. So that entire misses that we would've seen earlier when it would have thrown the exception would have been a number of different bits of information all wrapped up in this object or variable called EAX, which embodies the entire exception and everything that went wrong. So a developer would want to see that because then you would see the entire scope of the error and better be able to fix it. However, generally speaking, you'll get a nice message that is more human-readable and human friendly, which is what you'd want to maybe present to the user because then the user would get an idea that okay, that is what I did wrong. However, they're not getting the full shebang on the line number and all sorts of details about the code that the property don't need our shouldn't be seeing, right? Plus you don't necessarily want users. You don't know who is using your application. You don't want them to necessarily know that that line number 20 are doing this, etc. So those are ways that you can use to handle potential errors in your code. Because we're not perfect. Sometimes you write code and we don't realize that we're doing things that might fail, especially when you start writing bigger applications that have other dependencies that icon a database or on connecting to the Internet. If you try to connect to the Internet, the Internet isn't on, then you have to catch the exception and handle it in a way that user doesn't feel like your program is not written properly. 20. Arrays: Welcome back guys. In this lesson we'll be looking at arrays. So you can start off by creating that project that we need. I call it arrays and then we can get down to business. I have added some comments just serve as guides as to what we will be discussing in this lesson. So an array represents a collection of values. So we had a little exposure to an array earlier when we were looking at our string manipulation operations. And if you do remember when I was showing you guys the split, there we go. Moodle seen those a square braces or square brackets. And I said that that meant it was a collection of string blocks and we had to navigate through it and voltage at this point because we would discuss it. Well, that time has come. So let me just close all of the tabs that are not absolutely necessary. And just by middle clicking the tab, it will close. So I don't know if I showed you guys before nobody. If you have a tab, open our block of code open and you wanted to close it. You can click the XES week and also middle click the tab, it will close. Let's get started with our definition of an array. An array is a collection of values. For instance, if we wanted to collect, see the grades or five students, then typically we would have to end up seeing Edens green. One is equal to and then we have to do in grade two and grade 345, etc. That is not very efficient. Then what if the class goes to ten, then we have to come back in our program and make ten again. The point is that it's not very efficient when we have to have different variables like this to store those values. So what happens is that an array would be a collection of values towards one goal. If I know I want grades, I can create a collection type for grades. And then what we've talked about, fixed size, it means that I know exactly how many grids I want. Because if it's across all five, then I want a collection of five grids. To define that kind of construct. I would first defend the datatype for this collection. And generally speaking, you can use any datatype if you wanted a collection of names, it would be a string array, just like we saw, we have the string in a string manipulation. Listen. It could be a double collection of salaries, etc. So grades is just merely an example, int, and then you use your square braces, then you give it a name. So this is my colleague, Norma Ari. I'm calling grids. And then I can see z equal to new int. And then using square braces, I would say what value I would give you C Visual Studio suggesting Maxwell it, That's not what I want. I don't want the maximum colleagues on because that could crash your computer. But I did say I want five, so I'm going to put five semicolon. This means that it's going to go into memory and reserve five spaces for me. All right, five space addresses will be reserved in memory, all called grids. And then what will happen is that each one would have a number associated with them. Since grids space, one grid space too. But then the numbering for RAs usually starts from 0. So remember World War during the for-loop, we said we start from 0 and going up to one less than the exit number. So if the size of the array is five, then the cone thing will be 0. Then 1234. And that's it because that is 12345 species in memory. All right, so that's one part of arteries that can come off as confusing. But once you get used to understand, once again, the size is five, we're reserving phase species. But each one will have an address from 0 up until one less than that number. So if I see this like a math equation, if n is the size of the array, then your array has addresses from 0, Tooele minus one. That's me trying to sound like a math genius right there. All right. So five space addresses would give you from 0 to n minus one, which is four. That's it for our ys. If I said ten, then it would be 010 minus one. So 0 to nine would give you the addresses. Now the thing with this is that I have to cover and change the value here. It's quite easy. I mean, if I wanted it bigger, make it 15. If I want it smaller, make it five. Whatever. No more species I request here. When the program executes, it will reserve that many for me in memory. Now let us, let us talk about adding values to the IRI. So I didn't say that you would have subscripts are what you call subscripts. Subscripts represent these numbers which represent the addresses. If I wanted to add the first grid, I'll have to say is called the array by name. Then add my square brackets and then call the address by value. So the first grade would be 0, which is the first address reserved for me. And then I would give it the grid value. Then I can do that again. Upgrades for one would be two, etcetera, etcetera. So Visual Studio is just making suggestions. These are not necessarily the values because obviously these are great. So maybe you scored 25, maybe students three squared 38, and maybe student four scored 45. Notice this is Student four because this is one, this is two, this is three, and then this is four. Even though the addresses are 0123 and I think we have exhausted way up 12, no right to enter the grades for all students. I would end up with lines, we can let this student 12345, all five students and they'll have their grades. But I can see that this is a bit tedious. If you think this is tedious, I agree, because if I increase this to 25 and you had to write 25 lines like this, it wouldn't be very efficient. Also, let's take a look at what would happen if I added fifth grades. So if I said grids subscript five or sixth grader other, I said you are 60. If I tried to execute this application so you can switch over to areas as your startup project hit your button and then look at that unhandled exception we just went through except on handling. Now I'm getting an unhandled exception. And this exception type is System.out index out of range exception. I need to see in that the index was outside the bones of the array. So this is basically saying to me that you have five species. You asked me for five species. Why are you trying to put in a sixth value in something that only has space for five, that index out of bones array. Basically seeing that you're trying to access a space that does not exist inside the bones of the array. All right, so that is why it's very important to appreciate that the numbers go from 0 to n minus one. If n is the size of the array, that is very much illegal. Know another way that I could've assigned these values would be in one line like this. If I said grids would be equal to a new int. And then provided curly braces and then proceeded to put in these values. So one mod 2538, **** 4554. And that will be a nice one liner to assign values. So I wouldn't need six lines. I could have done it all in one line because of course, just have to initialize the array here. Let's just comment this all just pretend I could have initialized to have that number of species. No. Let us say that we don't know the grades of fronts were writing an application, which is probably going to be the situation where writing an application to allow users to provide us with these grids. So I mean, typically you wouldn't want as an IT person to write a program and then until you use those all, come and tell me what degrees are so I can enter them for you. You don't want to give them the power to be able to enter the grids themselves, someone to come in. Then we're going to look at whole. We can write a program that allows the user to go through and insert each one of these. So we're going to use loops in a more practical manner. No, Not just an example manner. So we actually did something like that in once again, our string manipulation exercise, where we had the IRI and you wanted to loop through our array. Remember that? Wanted to loop through the array. We can do something very similar to that. So I'm going to see for top tub int I, remember I is just my counter is equal to 0. So here's a very important point again. Why we start the cone to 0, because our array is going to start at 0. As we consider relevance. The next. Is that you can always see to whatever number. But then this by hard-coding the number like this, you don't know if tomorrow this is going to need 15 or 55. So when you hard code the number that you have to remember that every time you might end up changing the size of the array, you have to change the for-loop, which you might forget. We're all humans. So that is why we would probably want to use the array dot length, whatever length that ends up being. We'll just get that length during the runtime. And we know that we're going to N minus one of that length. And then we have our incrementer. Know after we have written all of that code, we're going to prompt the user to enter the grades. So I went to say console dot readline. Each time the loop goes around, I want to prompt or users enter greed. And I'm just going to do console dot write so it doesn't, didn't want line. And then I can say grids with the subscript of whatever value of I is. Alright, so let that soak in a little. Remember that initially I could say give me this exact address and I can put in the number. All right. No, I want it to be a bit more dynamic. I don't want to hard code it. I want it to be dynamic. So I already know that loop is starting from 0 and it's going to add minus one of whatever. However big this Ari's. So I can rely on as a, as a counter to go from 0 till the end of the array, one-by-one, just going to go 0, then one, then two, then three, then four. We saw that with the for-loop works. That's the counter in the for-loop works. Here. I'm just going to say, give me grids to the subscript of I. Right? In that I would like to store, I don't want to say convert to int 32 and get the value from the user console. Console dot read line. I'm seeing each time you go through for each subscript, go and get me the value from the user's input, convert it into an int and storage instead of my array. It seems simple and straightforward enough, doesn't it? Let us see how that would work. So when I execute and jump over to my console, you see here it's pausing. It's just waiting for me to enter grid. So this would be entering the grid into grades subscript 0, since it's the first run. And in the first grade I had was one look at what happens when I press Enter looped. It went to the tool, went to it incremented the counter. I know it's at the second subscript space waiting on that grid value. So this will be 2538 and then 45 and then 54. And then look there, it asked for was 001234 species. The IRI, if I increase this still 150 up one to one less than the iris space. Nice and simple. Know that we have collected the values. Let us look at hold, present them back to the user. So I'm guessing, I'm hoping that you realize by now that the easiest way to traverse an array is to use a for loop. So I'm going to put some more printing around these exercises. So enter all grids. That's just the heating to see where entering all the grids. And then this one is going to see the grades you have entered are the grades you have entered, are you have entered. Then we're going to print them out below. Once again, moving forward FOR loop, just right for top tablet it generated that stub. We're going to go for the length of the array. So array name dot length. And then we're going to see console dots, right? We're going to just simply print grids. The subscript of I. One is going to be filling it on one is just going to be regurgitating it to the screen. This is a rat lands. We will see them one-by-one. So let me test that one old with you. We see Inter grid. I'll just put in some random grid values. Then after entering them it pulls. The United States agrees you entered our 1020 to send the same order that I entered them. This is the same order. They're printed out because it's a structured collection. It knows what was first, what was sick on, what was third. If I wanted to print a specific one. I could easily just say console dot write line, and C grades with a subscript of C. Three. That will give me the fourth elements no matter what, it will always be the fourth element because that's how I can access it easily if I run this application again, wouldn't prints all degrades. Yes, you will print the first grid to enter, then it would print the fourth-grade hit Enter, then the second grader Enter then still the fourth grade. Because instead of being dynamic with the address, I'm always looking at address number three. All right, so that's really how arrays work. So when we move over to a variable size arrays, No, this is when we're talking about a situation where you may not necessarily know how many grids are to be entered. So I can actually define an on-site sized artery as well. Let's start off with giving it a default value. So if I said int grids, Let's say if I know agrees just so we can change the name. So int final grids in square bracket, final grids or you know what? Let me try a different data type so we have some coverage. Let's try a string this time. So string student names is equal to know. Remember, if I say new string array of five and locking it into a size. All right? The thing with these is that they always have to have a size. They're not dynamic. You have other collection types that are dynamic. Button is not that dynamic. You always have to tell it the size. So even though I said variable size, it's not really a variable size in the true sense. Instead, what would happen here is that I would have to see new string RE, not give you that defined size. You'll see that I'm getting there. The line represents most of us size or an array initializer. So I can use that initialization method that I showed here. Now what happens is that it will take its size based on what values are the number of values being put in. So I can see a test, student one, etc. So at this point, student names is an array that only has a size 4123. So there might be times when you're initializing an array and you might be looking at the list, but you don't know the number to see. Okay, I have five here. It might be 20, maybe 21, it might be 70. To write some number that you wouldn't be able to compute just by looking at the list. Then this is where that kind of declaration would actually come in handy. Then what would happen is that you just go ahead and list them out like this. And then when the program executes, it wouldn't know that. Okay, I have three are 72 spaces here. I need 72 spaces in memory for my already called student names. No, as far as interacting with this RE goes, it's really the same principle. It will be the same printing all over the seam. Interacting on inserting values. Really and truly, I'm not going to spear the repetition of going through those. You already have these code examples. You can, here's an exercise for you to look at how you would actually print the values at the values to this RA and how you would print them out. All right, so I hope you took the challenge. If not, then here it is. If you wanted to try and she'd pause, don't look at what I'm about to explain and try it yourself. But pretty much I would have just replicate that to see him for loop. So here I said enter all that should be names. Literally I copied and pasted enter all names. And then for each, sorry, for int I is equal to 0. I is less than student names dot length. And then we go in enter name and then student names with a subscript I is equal to, because this is a string, I don't need to convert anything. So I can just say console dot, read, line. The same way when I'm printing, I just have the same kind of for-loop and I'm just doing a console read line on student names with a subscript I. So that's really it for arrays. When we come back, we're going to be looking at lists, which is a dynamic list or collection type here in C-Sharp. 21. Lists: All right guys. So we're coming off the heels off discussing areas and I just learned to do a quick recap so we can look back at what they are. My personal definition of an array is a contiguous, homogeneous collection of data. Contiguous meaning that they are, they're side-by-side. So you have RESP S1 are just like, Well, I'm writing these pipes beside each other in memory there. All right, beside each other, pretty much. Just going down the line like this. So your data is stored in a chain like that, that's contiguous. And then homogeneous, meaning that you can only have one data types aqua icon to have an array storing both strings and integers. So it's either going to be in or it's going to be strings, etc. That is, what's an array is not one of the limitations of an array is that it always has to know its size. So it's hard to be dynamic in an institution where you don't know the size upfront. Because you're either going to define it with a space that is big enough to possibly cover every scenario. But then you're going to be reserving 255 species in memory when you might only use ten. That's not very efficient. That's whole computers get war, no time crash under heavy load from programs because of decisions that those, the alternative would be that you don't know the size of front, but based on the data you're providing, you can infer that is still not very efficient because you have to have everything entered from the get-go to then start using it. What we want to do now is look at dynamic collection type called a list, and that is available to us in C-Sharp. So I'm going to jump over, created this new projects, new console up and I'm calling this list collections. Of course we're using dotnet six and we create this new console app. When we talk about lists, the syntax is going to look something like this one. We define that we want to list. And then I say I wanted to at least off what datatype, the datatype here, just like with the array, can be anything. It can be at least of string, it can be a list of integers, etc. So let's do strings. And I'm going to call this one names. Then I went to initialize it to a new list of strings. You'll start seeing that we're dealing with far more complex types than just intense on, because you're starting to see that we have to be seeing equal new design that when we go over to the object oriented exercises, you'll start to appreciate why some off the variable declarations have to look like this as opposed to when we just see string is equal to that. We're getting a bit more complex, but baby steps, but this is all we declare a list. Like I said, this is once again contiguous homogeneous collection, except it's not fixed to us as initially. So instead of having one variable called name, we're creating a list of potential names. Let us look at how we add values to our list. Instead of like areas where you had to use the fixed point because I can invariably say names with the index name 0 should have the value here. I can't do that. Lists allow you to do that because really entry will at least is built on top of the general construct that is an IRI. So it's like, here's a big word nor an extension of an array. So they saw the limitations with the area, so they made an extension of it. But at the base that we can still do certain things that would allow you to do. But then they also made other functionalities for you. So you saw that Visual Studio was suggesting to me that I see names dot add name, or add whatever values I could add that value off my name. So these are two ways. Know the difference between these two is here I have to know the exact address that I'm adding the name tool, which I cannot know during runtime while the application is running. I don't know if 50 names went in already are only ten. I don't know. So by trying to access an address, I might run into the problem of accessing one that does not yet exist because it's only as ten and I'm trying to put it in space 50, or I will put it in space 50 and then end up with empty spaces between 10501149 will be empty. Once again, not efficient. So we would want to rely on the program, the method, sorry, that has been provided to us called dot AD. We see list name, which is names, names, dot add. And then we give it the value, will know that it should put it in this space because this space is the next in line. If one gets removed, it all automatically reorders. So you can actually remove and add as many things as you want. I can remove Trevor. From this I'm sorry about that. I can remove trouble or from this just by seeing Dr. move wherever trivial or using the list of dates the first star to stick on our third, it is going to go ahead and remove it and then reorder everything so that the address is 0 to length minus one are always intact. So lists are far more dynamic than arrays. If you try to remove or MTO DSPS in an array, we're doing runtime, it just won't work. Okay? All right, let us look at how we would add values more dynamic bodies. So I'm going to write a little console. And I'm just going to say enter names. All right? And then here I'm going to use more like a while loop. Why am I using a while-loop? Because I don't know the number of items that I want. So I can't go by our counter. If I wrote this program for a school, either programmer can't assume that the school only has 100 students. They might have ten and they might have a thousand. So I can't be using a for-loop to say, go through and do this for that many times because the length here is going to be determined by the number of things that goes in. A while loop would be better because then I can a condition through which they can exit this operation. So remember that the while loop or even the do-while loop, those are condition-controlled loops, right? So I can see while name, let's say name, so we have string name. You can redefine it already. Really curious if you had erased it. And let's initialize the string dot empty instead of the empty string manually. And then I went to say while name is not equal to the value negative one. All right, so I'm going to show you now how we write programs using condition controlled loops. You always have that exit condition and you can write this in a number of ways. You could write name is not equal to negative one. You got to also write this name dot equals. There's an equals film Shaun on a string they can use when you want to compare it to another string. All right, I don't think I mentioned that with the string comparison earlier. So you could say name equals that what you wanted when it's not. So you can see, not all right. You can see is equivalent to false. Oh, there's so many ways to write code, once again, half to explore. All right, so that's one way to write it. I'm just gonna show you all the ways to write it. Then you can also just see not this explanation saying not just that not equal. I'm just saying while this evaluates to false, while it is not equal to negative one, then continue. Let me leave those to code some blues there for your reference later on. I'm going to proceed with this one. So while name dot equals that is not true. That's what that exclamation sign means. Then we wanted to continue looping. I went to ask the user for the name. I'm going to see console dot write enter name. And then I'm going to say name is equal to console dot read line. So I load the user to enter the name. And then I'm going to see name, dots, Sorry, names that isn't able to list dot add. There we go. And we're adding the name that has been entered, which of course is a string. So I can just add that name as it is a string. This is saying know that it's a possible null. So that means that if the person didn't enter anything, do you really want to enter an empty string or something into the area of names are the list of names rather. So here's where I'm going to put an if statement. So know you see that this is getting more complex as our program, as we expand our horizons, we're starting to look at how we put an if statement inside of a while loop and how we're interacting with that list. This is what we call nesting when you have one constant control structure inside of another if statement instead of awhile is an nesting. All right, I can see if a string is null or empty name. So let's do this. If it is not null or empty, and look at this node and it is not equal to negative one. Nice and complex this if statement has gotten, then we can add it. Let's go from the top. While our name is not equal to negative one, which it won't be because we initialized it to an empty string. So it's empty. And this is, this pre-check is going to pass because it will not be negative one before it hits here based on the way we wrote or program. Then I'm going to say enter the name, accept the input from the user. Then only if the input from the user is not null or empty and the input from the user is not equal to negative one. That time we should add it. That means if it is empty, then it will not execute this if block, it will fail on that condition and then it will come back and check. But then this is still not negative one, so it will come back into the loop run again. If I enter negative one, then it will fail this check because now it's negative one, so it will still not enter, come back, and then it will exit. All right, so this is how we would use a while loop to ask the user for names until they are finished. Because when I'm finished, I can put in negative one. So this is what we call the exit criteria. And it's usually an obscure value relative to the context that the user would never put in by default, I mean, who puts in a bunch of names, inputs in negative one. So let us try that one out. So this is list collections. Let's start. Alright, so here we're being prompted enter name. So I'm going to enter trope or I went to enter test. I went to enter Matthew. I went to enter John. All of those values. Notice it just keeps on going. I'm just going to keep on typing and pressing Enter. It doesn't nor cure. It's just accepting the values. And then when I personally negative one, that is when it exits, That's the soul. No, you would actually be able to enter values onto the user is satisfied. If you want, you can put on another little prompt here to know when the value was entered versus when it was not entered. Because if it is entered and you could see name was inserted. So I can't just interpolate this string. Then just see that name value was inserted, successfully. Added, successful. Let me see, I added. All right. So then the user would get some feedback. Yes, you put in that name, it was added successfully. Or rather you'd put that after it was actually added. It was added successfully. Then that is how we fill our list with values. Now, how do we print our values from this list? So print values in list. Well, we have once again a few options. We could reuse the while. I think it takes a lot of coordination to use the while. So I'm going to skip the while example, but we already have a way we could do it in the form of the for-loop. It. So remember that lists are built on top of the construct of an RA. I could actually just write a for-loop that goes from 0 to the length of our list. So the list is called names and I can see names, thoughts, cones. This one doesn't have a length, but it has cones. Cones gets the number of elements. If you see the right up there from Visual Studio, gets the number of elements contained in the list. Alright, so like I said, sometimes what you want is not necessarily presented to or you might overlook it. Sometimes I end up scrolling onto some, I eliminate some property or some method looks like what I want. Visual Studio in more recent times has starred the most used methods and properties, and you'll see them at the top. Even though it's alphabetically ordered, you would see certain ones at the top. So like cones is at the top because I figure, well, people usually want to know the number of things in our list. Dot colon t, so you get it. It's there for you with, I raise its dot length with lists. It's thought cones seem that effect. We're going from 0 to the cone to minus one. Then I could easily just say console dot, write, print, buck each name called the list bytes name, and then give it the subscript of I, will actually iterate through that list for as many items as we're entered. Because remember, open didn't know, we still don't know how many items to expect. That's the firstly that you can do it. So this would be printing. Let me just do console dot write, line printing. Let me get my spilling rights. Printing names via FOR loop. That's what this first one does. Now the reason I'm specifying for-loop is you can also use another type of loop and one that is specially designed for this kind of situation, which actually got an honorable mention when we were looking at repetition statements, but I didn't get into it because the time wasn't right. And that is the for each loop. Now we know how to, or nowhere going to look at how the for-each loop, right? So I'm going to say console. I'll just duplicate this slide here. And this would be a foreach loop. Now the for each loop, you start typing for each and then you press Tab twice and it generates that stub for you. So for each, and you'll see it's seeing var. We look at what var is later on. What I'm going to be strongly typed here and say string because it is a string collection. String. Then we see item. What is the collection? We have to call the collection by name, the collection here he's over at least, which is names. It's basically saying for each entry in this collection, for each item in the collection of names, it could be more specific density for each name in the collection of names, but I can't do that because I already have a variable called name, so it would cause confusion. That's fine. I'll just leave it as item. My point is that this is going to go through whatever number of items are in that collection, whether it's 110105 thousand, will go through each one. Store it here for the runtime of the loop. And then each time it runs, it gets the new one. You can do whatever you want to do with the new one. Like I said, we wanted to print them. I'm just going to say console dot, write line. And all I'm going to do is print item. All right, That's all that it's really doing. That's a for-each loop. The for each loop is perfect. I don't have to worry about the cones. I don't have to worry about an exit criterion. All I have to do is say for each some variable in this collection, do whatever you need to do. Nice and simple. All right, so let us take a look at what this will yield. I went to enter a few names here, so we see node seen ********* added successfully. Bought I did a console dot write instead of R console right line. So that's why it's printing all that out, but I think we'd know that by now. So I'm not going to stress that one. I'm just entering some names. After entering all of those names, when I press negative one, you'll see that it went through the for-loop, printed. And then it went through the for-each loop and print it right up. To me. The foreach loop is just much easier to formulate because it takes a little less coordination. But there are situations where you wouldn't need a for-loop with the list, but context determines your execution most of the times it's good to know the tools that you have in hand. But the which one to use when is usually determined by your needs in the moment. That's it from me on the topic of lists. I want you to experiment, try lists with other data types, like arrays with other datatypes, and write other programs to accept values. Try to write a program that accepts multiple arrays. Or at least you could have names, student names, and the grids. And then you write a loop to enter both, and then you print them all back, get creative and explore. 22. Introduction to Classes and Objects: Hey guys, In this lesson we're going to start discussing object oriented programming. No, I've said before that C-sharp is an object oriented programming languages. And there are a few of them out there. Java is a very popular one. Python, Ruby, C plus, plus. All of those are also object oriented in programming languages. So the difference between object oriented programming languages and other programming languages will be the object oriented programming languages allow us to create our own datatypes. And we do that through the definition of what we'll call a class. To get started, let's create a new project and we're calling this one classes and objects. So go ahead and hit Pause, created the project. And we can start looking at what the class is. We have interacted with classes upon to know Console is a class. And I would have pointed out that based on the color coding, you would see that there are classes, right? So Console is a class. When we looked at least collections. We also looked at a class, and that class is called list. And I would have shown you that the declaration for this kind of object was slightly different from one. We add our irregular datatype. We would just say data type equals whatever. List is actually a very specific datatype that was created. That's not one of the, what we call the primitive data types. Primitive datatypes would be what we would have used when we started off. You don't int string, char, bool. All of those are primitive. Notice they're all the same color. Preventive because they're as basic as datatypes can get. But they don't necessarily provide all of what we want. So in order to capture a certain beats off inflammation like when we had to do the program getting all of these bits of data, we had to have 12345 variables to collect data on one person. We got to have full name age. But what if I wanted one representation of a person? That is where creating your own datatype comes in. So object or into programming has to do with creating your own data types. You're a datatype since you're the one creating it, you can determine what properties are, what methods can be involved. We do that through the definition of what we'll call a class. A class is a blueprint of what the object is going to be. The object is the manifestation of the class. So think about it like with a host. When you are going to be building a house, you have to put it on paper, you have to outline, we're watching goal, how big each room should be if everything is done in a visual representation, a 2D representation, that is the blueprint. However, when you build the host, that is the manifestation of set blueprint. And then if you have multiple holes is built off that blueprint, then you have multiple manifestations. So if we were to do that in OOP, the blueprints drawing would be our class, That's the outline. And then each host is an object of the class. To define a class, we seem to use the keyword class, then we give it a name. So if I'm using person that isn't name of the class, then I open and close. My brief says, my curly braces know in defining the class we have to give it properties. So you see Visual Studios here making a suggestion. I'm going to do it manually so I can explain what each part means. Properties refer to the, let's say the knowns, the object. So in the case of a person, what is unknown on data person has ij is unknown, so that is a property of a person. The name is a property of the person right there. Address every bit of information on a boat, a person in this context, or a boat or whatever the class is, every bit of information is indeed up property. To get the property firstly, give it an access modifier. So you have different ones. You have public. That means 170 cannot type person, I can access their whatever is public. Then I have to give it a datatype. So public string, and then something that is publicly accessible level most persons is their name. So in reality, name is a very good suggestion. I know the thing that's. Probably be publicly accessible about a person would be there each because each would be more like an int. And then I would say age. And notice that it has this get and sit open curly brace and then get semicolon, and then sit, get semicolon, then set semicolon and then closed curly brace. These are what do you call accessors. So these allow you to get the value involved here are stored here. And this one allows you to sit the value stored here. So by seeing get to unset, it means that once I'm interacting with a person that I have leverage to get what their name is or sit what their name is, gets what their name is, sit what their name is. Alright, so class, give it a name. I noticed just by seeing class here that takes tier that I have written. Null has the same color as console and list and all the others because it's only this is me creating my datatype. This complex data-type is making use of primitive datatypes inside. A person has name, has age, might have other properties. Before I move forward, what I'm going to do is split the salts. So generally speaking, you don't want to just store name, you wanted to store firstname and you want to store lastName. Notice the naming convention also, I'm not using common letters, isn't if I use the common letter, it will work. There will be no problem. But then if I go here and control dot Visual Studio suggesting that I use a capital letter so far properties in a class, it is suggested that you use the capital letter, that's just a standard. It's not that only works. Bits are one. We are at. The elbow is just a standard and I'm always pointing old standards and best practices to you. Public is the accessor that's allows me to access anything about this person, the first name, the last name, and the age. Now, another thing that I wanted to bring to the fore before we even started looking at objects. I'm always showing you best practices. You don't necessarily want to have your class defined inside of another class. So each class should really be in its own file for contexts. And I'm just going to collapse everything here on the Solution Explorer. You can do that easily by using this button collapse all, it just collapses everything. And then I can target this file open this file that is here specifically by clicking this sync with active document. Some more keyboard shortcuts, Visual Studio Tips and Tricks coming out to you right. Here is our program.cs file that work are in the working and this is a program.cs file. It means that this is a class file dedicated to the program. I want my own class, my own datatype defined. I don't necessarily want that defined inside of the program. There is another principle that we adhere to call single, single responsibility principle. This principle basically means that let each unit, as far as practical, have only one responsibility. Our program.cs file should not have the responsibility of defining our class. I would want to put this in its own class and easy way to do that, thanks to Visual Studio, would be two, while you could easily just right-click Add New Item. Then you could say you want a new class file and he could give it the name. So I went to see like person. And then it will generate this entire code block showing you the namespace. So remember the namespace is the name of the folder. All right, So our project discusses an object, so that's our namespace. And then it generates that method stub with another access modifier called internal public means that anybody can access it, but internal means that only other files instead of the same project can access it. Alright? So I could easily do this and then this is where I have my class definition. No, I have this class defined in a completely different files. So if I wanted to know where my person crosses, I need to find it. If my program had a thousand lines of code, I wouldn't have to comb through all of them to find the person class because I can just go and find Person.new ECS. And this file has a single responsibility of dealing with anything related to the person class. All right. No, i keyboard shortcut to do that would have been to do control dot. And then it would actually ask you, do you want to move type to person dot CSS? So it would actually suggest that hey, I can just move all the code to a new file for you. If I didn't create this new class, let me just erase it just to show you. I can just Control dots and then move type to person dot cs. Then it would actually just do a cut and paste for me and create this new file formula. And there we go. I'm just showing you the different ways that you can do that. Once again, public. Who have public that can be on the class. You have internal. That means it's not public to the world, but it's public to anything inside of the same project. Then you'll have private, which means that you need various special permission to access it. And even Visual Studio utility, you can't have something that's private here and everything else is public. So you don't generally see private classes, you usually will see public and internal. So I went to leave this one as public. And then all of these properties are also public. So now that I have a class defined, code-wise, interact with it in my main program. Let us say that I wanted to write a program that allows me to fill in the information for a person. I remember person could easily just represent whatever object and properties of that object you want. If it was a box, it could be length, width, height. If person who was to be a student, it could be first name, last name, age, and greed. Remember the whole head the trouble of doing one array for grades on one array for names. We could do everything inside of one big data type called personal or whatever it is. Once again, it's just a blueprint. To get the manifestation of set blueprint, we would have to do what we call an object declaration. So now I'm going to start seeing object instead of variable plus variable tends to refer to the manifestation of primitive datatype. To get more complicated datatype would say the name of the datatype, which is person, called the name of the object, which I can say this person. Notice I can name one with the capital P and one with a common pea. And that's really because I think by nowhere realize it's very strongly typed and it's case sensitive, so capita appease entirely different from common P. Then I'm going to say is equal to a new instance of the class. If that looks familiar, then good. It means you are paying attention when we did our list, list, whatever names is equal to a new list and open and close brace. Whenever you're dealing with a class that needs to be declared, this is what it's going to look like. Person. And then the name of the object is equal to a new instance of that object. Guess what? It can also have multiple instances of that object. So you can have person one, person two. Because the reality is that you have multiple persons in the world. What we all have in common, however, the properties defined, every person has a FirstName, LastName, and each, if not, I stand corrected. This is the general blueprint and then these are all manifestations. Offset blueprint. Know a shorthand way to write this in C-Sharp, Eight upwards or 900 words would be to just say new. So you don't have to write person who is equal to new person again, you can just say person is equal to person equals and then new. That's a nice sharp and we let us work with one person for null, let us write an application that is going to accept the information about this person. And then it's going to print it back to the screen that this is dispersed. Information is I can see console dot write line, enter, firstName. So these are things that we have done. We know how to prompt for the FirstName. What we didn't know before is hold to store everything inside of one object so I can see a person. Notice person is the object that we have defined. I can see a person dots. And when I say data, I have access to a bunch of methods and properties. So how do I know methods different from properties? First hint is that in the intelligence the methods are going to have that cube. Then the properties are going to have that range. So our property represents one of those variables that's I would have defined here. Method would represent what we looked at methods already. So we can actually do methods, we'll do that in a few. So just by having lactose, there are some default methods that we would get like two strings. So I did say before that every single object in C-Sharp can do toString what is not always practical. It has the equals, does get type. It has a bunch of built-in methods. I'm going to start off with the easy ones, which are the properties that I know I need to interact with. So person dots first and the meaning when you create this entire object, which is a collection of these three variables, I wanted to set the first name to have the value coming in from the console, console dot read line. It, that's number one. Then I want to enter last name will be the same principle. So person dot last name is equal to get the value from the console. Then I wanted to get the edge. So enter. Then we say Person.new edge, and then age is an integer. So if you said we need to convert, then you are absolutely correct. So we need to see converts dots to int 32. Let me get my spelling rights to int 32. And then we wrap that up in parentheses. And there we go. No, I'm filling in the information for this person. This is courtesy of the get sorry, off the set. The set allows me to do this. If I didn't see that I can sit the edge, I can only get the age. Then I'm going to get an error when I tried to do this assignment because now it's saying that there is no, see it's read-only. I cannot be setting a value on that property. All right, so that's why I get ten sets are important if contextuality are important. So you may not necessarily want somebody to sit the age. Of course, once again, I'm just giving you the concept. The implementation is relative to your situation. Firstname, lastName, age. And we can enter each one directly into the properties as provided by our object of type in-person. Now let us look at another property like maybe the salary. Most people keep their salaries private. That's not something that you'd be able to google me and find very easily. Within that context, you wouldn't necessarily see public salary. You would see private, the datatype double and salary. And generally speaking, when you are doing a private, what we'll call this a field. So these would be properties when public. Generally, when they're private, you call them fields, just some jargon so you can appreciate the difference. So generally speaking, with the fields, you would actually use an underscore here to denote that this is supposed to be private. So if you were just looking through somebody's code and you saw to underscore the general guideline would be that are the general theme behind that underscore preceding the name would be that it is a field, it's private. Whereas when you use a capital letter, it means it's public. So that's just that little thing that you can look out for. Once again, another good practice to have. When I tried to interact with anything that is private, like over here, if I said person dot salary, notice it's not even coming up in the intelligence because C-sharp is saying this is private, so I'm not even supposed to show you that. If I tried to access it, if I tried to interrupt with it, it's going to say, boy, it is inaccessible due to his protection level. I cannot help you. It is it is private. You can't just interact with it like that. So that is another thing that you can look out for when it comes to private and public settings on your fields slash properties. When he comes to our private fields, that's when we start talking on both methods that would be needed to interact with them. A method would represent more like a verb. So I did say that properties will be like knowns. These are things that are on the object. What didn't, what can the object do? A person can walk, a person can run, stuff like that, a car can drive. Those are things you can do. Those are methods. Anytime you're thinking about something that is doable, that would probably need to be defined as a method as opposed to our property. So let us say for instance, we wanted to be able to get unset salary. Those are methods you're getting is verb, setting is a verb. We have it as a private. We would need methods to help us to interact with it. What I would do here is define a method. We already looked at how we define methods. What do we probably didn't do was put on access modifiers on the method, right? So if I'm going to set the salary, that means I don't need to return anything. I would want something like a void method. I don't want to call it set Celery. Celery. Your job is to give the private field a value. Let us say I'm going to set it to 100. Once this method is called, salary will get the value of 100. How do I retrieve this value? Well, I can do another one, whereas the public get salary. And this time I'm going to make it that value returning because I want to retrieve what the salary is, then all I'll have to do is return salary. All right. Look at it, no private field. And then we have methods to interact with the private field. We have one to set its value. I don't need to do anything. I don't need to return anything after setting the value, so I'm just going to do avoid. However, don't here, I'm going to be sitting it. Sorry. I'm going to be retrieving it. So if I'm retrieving it, that means it needs to return it. And if it returns it to the camp before the test to be the datatype off whatever I am returning, which is a double. Alright, just showing you how everything is connected. So because these are two public methods, I can easily say person dot, and then look at this null set salary's listed. It gets salaries also listed there. They are one public, so they are visible. And two, they are methods. Notice the cube. Alright, I did describe that the cube represents that it's a myth. Let's see if I call it sits salary here. Then I wanted to print what that salary is afterwards. I'm just going to see salary is. And then I'll just do interpolation and then look at the second person, dot get salary. For us not get salary is going to retrieve what the salary is and that's going to be printed in the console dot write line. All right, so what we can do is test the salt. Before I test it told though I'm going to create some other lines. So I went to see a first name, last name, and age is. And what we will be doing is printing the properties. So person dot first name, person, thought, last name, person thought age. And then these are properties. And then this is a method, but all of them are related to the same person because we're entering the information for one person. So I'm going to change my startup project that causes an objects. And then we're going to take this one for a quick spin. When the program executes into the first name, I'll use my own name, last name, age, let's say I was 45 years old. So nobody's going to print back everything about that person. First name, last name is Susie, everything is being stored on the salary was set to a 100 courtesy of our method. But that's not the reality because we are hard coding the value, right? So my salary is not your centers. So when they're entering you as a person with your name, they need to enter your salary. What I can do, it simply is one creates a local variable that I'm going to call salary here in the main program. Then I'm going to accept input from the console. When I get this low cost salary, that is the salary that I want to use the SETT, the person's salary. We looked at using parameters in our methods. I'm going to modify the set salary method. And already there was press F12. So when he'd wanted to jump to a method, you want to navigate to this method, you just click it, press F 12 on the keyboard and it jumps over to the definition. So that's another keyboard shortcut for you. So from here, I can tell set salary to accept a parameter called salary. And we'll use that value that is coming in to sit the private field. All right, so that means no, when I'm calling set salary, it is know as an arrow because it's expecting a value so I can give it the salary which was accepted as user input. So user inputs, salary, we call a person dot set salary, ascend over that value that just came in. Then inside of that method where using that value to set the private fields. So whenever we asked for the salary, that is when we get back whatever was accepted from the user. That is full, you would have to interact with private fields. Another thing that I'm going to show you is maybe get the full name. Goes retina where getting FirstName, last thing. What if I didn't want to print firstName, lastName? What if I wanted to see your full name is, your age is, and your salary is, right. So I can easily put in another method. It's up to me so I can put in a value returning method of type string that says get full name, get full name. This doesn't need any parameters because it will be interacting with properties that are already inside the class. So I can actually just tell it to return a concatenated version that we'll see. I'm going to interpolate a string showing firstName and lastName. Alright, so first name and last name, and that's easier, fullname, and that is what I want you to return. So anytime somebody calls get full name, it should return. That. A block of string with the first name and last name included. Know instead of saying firstName and lastName is, I can come in these lines. Then I will just create one to see full name is get full name. Look at that person not get foo name. Age is that I am going to give you a challenge on this point for age, what if you wanted to know what the year to person was born instead of just the each. You can take the age. And then you can create a method that says get to year of birth it and let it return the year of birth and print it back to the screen. When we talk about classes, objects, and encapsulation, I did see, I would explain what encapsulation is. Aggregation. One, the class is the blueprint. From this perspective, anybody looking at this, it doesn't know much about person. They only see person when they're interacting with the object of type person. They can interact with certain things. They don't necessarily understand how it works. That's what we call encapsulation because the inner workings of the salaries actually set, it's actually retrieved. They don't know that others seeing is get salary. Do they made simple I wanted to salary. I just call the sky. Gets salary. If I wanted to full name, I'll just call get full name. They don't know the hardware that's actually happening behind here. However hard or assume that it is, the person interacting with the object does not know. In the blueprint is where you define all the functionality, but the actual usage of it is supposed to be as simple as possible for the person using it. And then further to that, no one would talk about aggregation. It means that inside of this one complex class, we've aggregated a number of properties and operations that they can do. So from this perspective, in a few lines of code, they can accomplish so much without realizing how many lines of code would've gone in our aggregated to make it up in. Let us run through another test with this so we can see if we get by the full name and the salary again. I went to enter for VOR William's age 58. And then when I press Enter, I think it's asking for the subtler I didn't put in the prone for the salary. So let me put you in 2 thousand. And then Node seeing your full name is full name as given to us by that string. And here I'm seeing two spaces. Alright, so that's something we could look into. I think I put a space after one of them. That's why we're getting the full name. We're getting by the age and we're getting buck. That's salary value that we took via inputs. So that's a quick introduction to object oriented programming. Once again, practice makes permanent. So go ahead and get some practice by trying to figure out how you would calculate the person's year of birth based on the age that was provided. 23. Method Overloading: Hey guys, welcome back. We're continuing on our journey with object oriented programming. And I just wanted to mention a quick concept called method overloading. What would've noticed up until now in our interactions with cost is even before we started creating our own, was the fact that we could actually write or access different variations of the same method. This look at the console class. Console. Dot write line. No dot write line has 17 overloads. So an overload means that you have different ways to college. You could just call it empty, meaning null parameters. You would call it with the bull parameter, with a char parameter. And I think I'd scroll through and showing you all of the possibilities. This is actually a method overloading happening right here because it's the same method with the same name would see him return type. It's going to operate slightly differently based on the value that is being passed in here, whether it's a string or an entire chart, etc. Once again, encapsulation. You don't know, right line is working. You'll only know its inner class and it's a method that you call and you give it a value and you expect that is going to print out something to the screen. You don't know what to do to convert the Indians or the string or the W here into the string are what to test it with irregular stream. And all of those things, right? You don't know. At the end of the method overloading can be very important when you want to give your users opsins to carry out the same kind of operation or different options with the same method name. Someone to keep this one simple, but it's simply enough concept that with one example you should be able to catch on easily, right? So let's see, we're getting the person's full name here. I wanted to overload it to potentially gets their middle name as well. So I want an option where I can put in the middle name and get the full name with the middle name included. There's no property in person for middle name. So I'm going to do this from scratch, right? So let's say I have a string variable, I'm going to call middle name. I'm going to initialize it the string dot mt. I'm going to prompt. So earlier I did not add the prompt for the salary. I'm just southern. Get my spending right there we go. Enter the salary. Then I'm going to ask for the middle name. So I went to say console enter middle name. And then width for the middle name inputs from our console, dot readline. Once that middle name is put in, if it is present, I would want to get the personal full name with the middle name included. Otherwise, just give me the regular full name. I'm going to use an if statement and I went to make a quick decision. You've seen something like this. If string dot isn't null or empty. So if there is no middle name present, meaning the user did not put in anything for this input. Then I will print the regular full name. Else. I would like an option where I can give you the full the middle name and that gets included in the full name that's printed. Now, notice this one takes no parameters. That's how we defined it. This one, I'm passing the parameter and it's giving me an error. Why? Because it says no overload for that method takes one argument saying that I see you're calling this method, but I can't find a matching method definition that's supposed to take any parameters at all. So it's up to me no, to go into the class and make sure that it exists. So I can just go over to person, just click it, press F 12. And then I can create another method that I can make a public String, give it the same name, get full name. But this time it's going to take a string parameter called middle name. See that? This one, no, I can make it return the same kind of string. But I'm going to include the middle ear in the middle of that string, right? So once again, that user will never know that whether the difference was this complicated or that simple. They just know that they have an option to get the full name. And they have an option to get the full name with a middle name included. Know that I have these two versions of practically the same method. Say method because of the name. If I look back here, that error is gone. All right, so once I provide a middle name and went to do a check to see which option should I call them? Should I call on Person.new setFullName here or should I call on the one with the middle name? Middle name prisons. All right. Let us test that one quickly. Get the first name, the last name, get the age, get the salary, then the middle name. If I don't put anything there, notice it prints all my firstName and lastName. Let's try that again. I'm going to run it again and then see same thing. Age, salary. Then I do have a unique middle name. It's a Greek, it means reservoir, it means bread of life. Actually. I'm sorry. It's Greek, it means bread of life. And when I presented in the inputs, then I get that option for VOR, our toes Williams, right? If you want to make sure, let's do a little debugging session. Someone who puts our breakpoints on either one just to make sure it's going to call the cart one when we expect. This is another way. If you were doing it anywhere and getting the output that you expected, feel free to use your breakpoints. So forever Williams or just kinda do shortened to get through this quickly, no middle name. Press Enter and OTC called, get full name with all middle name because I didn't provide a middle name, I just press enter so it was not empty. And it's no calling this method heating that break point. So at that point, firstName is true for last name is Will. If I hover over the middle name, There's nothing there. It won't even show me anything because there's just nothing there. It was not sit. Right. So if I press F5 to let it continue with the execution and press enter in the console to F3 top. Then you will see It is No, I'm printing out as expected. And then just the same way. If I put in test user celery and then a middle name, then it's going to hit this one where it's passing over that middle name. That is a very simple example of method overloading. Like I said, it's something that we have been doing from the get-go with console.log wetland and some other methods. That's how you can implement it within your own class. 24. Static Classes and Static Class Members: All right guys, So we're moving on and we're going to be looking at another category of class types. And this one is called static. Static gas is one that cannot be instantiated. So when we talk about instantiation, it means this when we create an object of a class. Alright, let me, I should've done this earlier, so let me just show you, give you a code or reference to hold. It could also be done. All right, So what do you say new or you say new person? And later on we'll be looking at another keyword that we can use, the obscured a datatype. But let's focus on static classes so we cannot instantiate a new instance of the class. So we've instantiated our own class. We have to instantiate list and we would've had to instantiate to some extent the RAs when we did arrays or even the dead time so that those are all classes. Datetime is equal to new datetime. We had to do that earlier. A static class would be more like console. All right? So console actually gives us well static methods rather. That means that we don't have to see console creates an object is equal to a new instance of console to then access right line. Because there's no way that I could say person with a capital P B in the class type dot. That doesn't give me anything. It doesn't allow me to access any of the properties without instantiating it, which is creating the object or the manifestation of the blueprint. And then through the blueprint, through the manifestation on rather or the object, I can access the properties and methods. So we're going to look at creating a static class and how it could come in handy. Static class is usually used as a utility class, so I'm going to create a new class file. So I'm just going to directly call our classes and objects project go to Add New Item. And actually you can notice you have a short quotes here that just says class, granted, it's almost the same thing. He's going to bring up the same dialogue window and just focus on class for you automatically. Let us say, I call this util class date util. Date utils. No day to till. It's going to give you the new file, is going to give me all of the using statements. And once again, this is a traditional C-Sharp file. In dotnet six over we have access to minimum files where we don't have the namespace and all of those curly braces and all the using statements. Upfront. You can always clean these up by holding down Control and pressing key than E. And it will remove anything that is not needed from your files. So we don't need all of these using statements Control key. Sometimes you just wanted to file to show you what you need to see, which is the whole philosophy of six is almost over ****** with even these code blocks where the namespace I can remove those curly braces and just put a semicolon. C-sharp six will automatically know that this is the namespace that governs the entire file. So I don't need all of those breezes. Know that we're delving more into old PM showing you little things about hold the chord is laid out and how you can interact with it. You could actually do this in C-Sharp tin, granted, the way it was before it worked perfect. I mean, Visual Studio gave it to you so it must work that we also, all right, Let's focus on our class, internal class, and we're calling it D22. Know what if I wanted to calculate I wanted a method to calculate the debt based on the year value. This utility class is going to have a bunch of methods that just do things for me. So public. Year of birth. And then this year of birth class, sorry, method is supposed to return an int public into year of birth. Let's take integer, year or integer each. Let's start with that. Alright, so given the age, I want to return, what's your probability year of birth is? In this method, I'm going to do some calculation. I'm just going to return the time. Date, time dot no, year minus h so easily that is. So datetime dot know gets the current timestamp, get me the year. Off the core in timestamp and then minus the age from it and return that. That's an easy way to know your year of birth. Nice projection at least, right? Let's try another one. What if I wanted an overload for that? That's allowed me to also return a year of birth. So I'm still going to give it the same name overloading. But this time I would want to take your date of birth. Date of birth is the property, is the parameter that I want. Then what I can say is if okay, let me see what Visual Studio has for me. If the date of birth that you gave me is equivalent to null, then return 0 or tilapia. Otherwise, return the tough year, time, no, year minus date of birth year. Oh my gosh. That's lovely, but that's not really what I want. I want more. I wanted to just give you a buck the year because I said year of birth. So if you give me the time of birth, then I'll just return. What's your year of birth is right? However, I'm just showing you these are methods that the focal points is not really the methods. I'm just making a bunch of methods in this util class because I'm just showing you that, generally speaking, study classes are like util classes, right? So this one would determine your age based on a date of birth. And then I will just revert to the original suggestion. We're dead time no. Year minus the date of birth, year that you provided. Utility classes know on a normal circumstances to start interacting with these methods, utility methods, sorry, interact with them. If I wanted to use them instead of my program.cs, I would have to come in here and say datetime D2 till creates a new object of date utils. So notice now it's telling me that it could not be found. This is because the namespace was defined above the file and no other class in this particular project has that namespace. The namespace basically is a declaration to the files off the address. If that address is not included, then you use it. Simple solution, I'm just going to remove the namespace. It's not absolutely necessary, at least not in C-Sharp tenant on it seeks know that it's removed. I have access. Know if I needed to calculate something out, I have to say object dot. Then I would be able to access all of these methods. Accordingly. Year of birth versus the age versus what was the other one year of birth was overloaded. Sorry. I just remember it was overloaded, so know that it's overloaded. In intelligence here we're going to C plus one overload. So you can give me the DateTime, date of birth, or you can just give me the age of the person. Alright? No, static das removes the need for this instantiation. So to meet this static, step number one is you're writing the word static in the access modifier section. If the class is static, then the entire everything is in the class must be studying voted that way. The class is static, then the methods have to also carry that access modifier, letting the whole compiler thing, the whole program know that they are static. Though, you can have static methods inside of our regular class. Alright, let us see, know what the interaction would be if I wanted to find out, okay, Notice sold since making it static, this is not illegal. I cannot instantiate. Static type. Cannot declare a variable of static type. I can't do that anymore. Instead, I'll have to do is call this class. They do till then I just say dots. I didn't, I cannot access any method that is in that dress. Much local console works where just say console.log. And then I access the method I could easily print. Age is that. And then let's say a year of birth. And then I just say D22 dots, Dots, year of birth. And then what am I passing in? I don't talk about dates of birth null, but what I do have this on my overloads. I do have an edge so I can give you the age. Okay. So I can say Person.new age. There's a person's age needs to only what their year of birth is. That's basically it. Like I said, it's usually used for utilities. So any quick operations are operations that you might find yourself repeating a number of times. You can just create a static class grade the method, those, that operation, sometimes it's as simple as I'm joining strings. It could be trimming strings. It could be converting between datetime and integers, stuff like that. It could be a math class where you want to find the root, square root of stuff. You just create a class for that. Alright. Let us test this out and see how well it works. Alright, so I'll fill the social war. Williams, 5070 years old into celery middle name. We don't need that. And then you'll see here fullname is that age is that year of birth is 1965. So it took that age, did the calculation as we defined, and return that value. That's basically it. So that's how you would use a static class in a very practical situation. And throughout your journey with C-Sharp and object oriented programming, you're going to encounter a lot of static classes. So it's good to understand how they're built, how they're used generally, and when not to use them also. 25. Inheritance with Classes and Interfaces: All right guys, welcome back. In this lesson we're going to be talking about inheritance. So we're still looking at object oriented programming. Uncertain concepts are at least key concepts to get you ready for writing basic application. And for the second part of this course, where everything is focused on object oriented programming. Where we went to discuss inheritance by creating a brand new project, a new project, and console C-Sharp on where calling this one inheritance. Inheritance. So inheritance has to do with exactly what the word suggests to you as a human being when he talk about inheritance, it means receiving something from another source. Some persons are extremely rich because of their inheritance, which is something that they received from their predecessor. Inheritance has to do with shearing properties with somebody else, shearing my stuff with somebody else. In terms of object oriented programming in this concept, it means that we don't necessarily have to repeat certain things across types that sheer common attributes. So enough talking, let me show you some practical examples. Someone to create new class or at least someone to write the classes here and then we'll move them to their old file. So let's say we have a class that we can call it a 3D shape. Starts so this cloud shape, right? A shape. In our definition of shape, we're going to have at least height and width. Let us say we have a property. So a keyboard shortcut for writing our property is you can write prop and then press Tab twice and it generates that stub for you. We can have double height with a capital H, of course. Then we can press Enter at the end of filling that out. And then go to the next line and say propaganda tab, tab and then double. Then you press Tab to move from the W2, the property name, put that in. So let's call this one length. Then press Enter and that's it, right? Typically, shape will have at least the height and length. No, you have variations of the shape because triangles would probably have your height and length within they would also have, That's what we call the hypotenuse, so to speak, right? Cube. Cuboid would have height, would have length, and it would also have breadth? Or would we have a base class so-called obese grass of type shape. You have an access modifier called obstruct. This means that I cannot, sorry, this has to come before the word class. Abstract class shape means that yes it's a class. Yes, it exists but you cannot instantiate it. So remember, just like with the static, we cannot see sheep new shape. We can't do that. That's illegal because abstract cannot do that. At the end of that operation, when we have defined our shape class, I'm going to Control dots and move it to its own file. So move shaved dot csv its own file. So we are shaped dot cs. Noah want other classes that are going to share properties of a shape so I can easily create another class, public class, and I'll call this one cube. To inherit, I just need to see colon and then give it the class name that is inheriting from by seeing public class cube colon. It is inheriting from shape. Now this is complaining because of the inconsistencies with the, with the accessibility access modifiers. So this is public, while shape is not public. So if I remove the public here than it should be fine. There we go. If I made both of them public, it should be fine. Class cube, colon shape. Then here I can define my own properties. So the cube or a, we already have high to already have length. So here I'm just going to give it a width. Know what I don't need to go and define any specific properties. So even if I'd tried to define C double height again. C-sharp is going to underline it green. And let me know that well, you already have shaped dot height. So by defining height here, you're overriding the original one. Being redundant, you're repeating yourself. I don't have to do that. If I was to instantiate Q, Let's say I say cube. Cube is equal to nu cube. I can always. Let me move this to its own file. So Control dots and then move to cube dot CS. Yes, I would like to move it. There we go. So now I have an instance of cube. I can see cube dots. I can get access tool length, which is courtesy off shape. I cannot get toxic. It's the width which I just defined, and it can get access to the height, which is also currently see how shape, that is, what inheritance allows. It allows me to define one source of common properties and then reuse that source across multiple places. In. The reason I made this abstract is that I don't know what the shape is. Even if I was to say sheep is equal to new shape, what is the type of ship? Is the circle? Is it a cube? Crc cannot instantiate an abstract type of sheep. It's abstract. So the concept of a shape is indeed abstract, which is why C-sharp give us that abstract keyword. What is a shape? So the actual manifestation of a ship is one that we can quantify like cube, cuboid, rectangle, etc. As many other types as I can think of. So let's say I thought of also including tranquil class triangle. That's also a sheep. And I wanted to inherit from shape. All right, because they do have common properties, then our class called triangle is just going to have its own unique property called maybe hypotenuse. I might be able to slacking with my geometry here, but just work with me. So triangle is also inheriting from sheep. That's two fewer places to put, height and length. All right? So I can always put triangle in its own type. So single responsibility, once again, if we wanted to modify a triangle crowds in order to finance if we wanted to modify a shape, you know where to find it. If you wanted to modify cube, we don't where to find it. And the mean program is here. You'd notice that because I'm using inheritance, there's this, It's a symbol coming up here. This is called an inheritance margin, will actually allow me to jump between the base class inheriting classes. So if I modify the base class, and then from the base class I need to jump back to one of these cuboid triangle. I can always just click that jump over to cube. And it's a nice, easy way to navigate between classes that are inheriting from another. If you want, you can go ahead and write old console red lines and red lines and fill the cube and then do some calculations, right? But then that brings up another interesting point. When he comes to us doing calculations. We would have to know how to define the area or the volume or whatever based on the different types of shapes. Shape? Yes, it could have one method which defines as getArea. Sure. Public double get area. Generally speaking, for the area, you just need the length times the width. If it's a triangle, it's half base times height. And let's assume that the length here is the base times height. So you'll see that each shape is going to have its own way of getting the area. So it's not quite easy to just say, oh, I'm going to have one abstract loss and have one, it gets area method. That will work. Of course, you could just define gets era inside of each one of these derived classes. So we call those derived gases whatever is inheriting. He's called the derived class. Whatever is being inherited is called the base class. So those are the two keywords they can apply to your conversation. I can always see public double get the area for the triangle. And I can always see public double get area for the cube. But then if I go to another one, Let's see, I bring up another class. Let me just, let me do it this way. Let me be consistent. So let's say I have class rectangle. That's another shape that we interact with. And it's also inherits from shape. All right, and then it doesn't have any additional properties and then in this moment actually forgets to give it its own get era. So right here, I'm going to be very inconsistent because cubed can get the area, triangle can get the area. And I'm human, I forgot to put in the GetArea class or method, sorry, in the rectangle class. No. I get the area of the rectangle and I published my program. I sent you told to persons and then I'm getting this feedback, Hey, this doesn't work when I tried to with our tongues, work. This will support a built etc, etc, etc. That's kind of feedback that should employ you to do better. But my point is that there are times when this can happen. So that is when we want to move our inheritance from just classes, abstract class here, and then start looking at inheritance using interfaces. Interface is scaled down version of a class, but it's more like a contract. I'm going to show you an example of that. So I'm just going to write it told here. I'm going to say interface instead of class we say interface. And then generally speaking, the naming convention for an interfaces that you started with a capital I and then you give it the name. So i shape. That's the interface that we're working with. No, like I said, it's lighter weight class, meaning it can define properties, it can define methods, but rather it can declare them, but it doesn't define them. Just to buck truck. This is a function call. However, the definition of the function is the actual code that a function is executing. Let me jump back over to my person. So here's the definition of the function. Those are definitions to interface may not necessarily define it because the definition of get era for rectangle is going to look different from the definition for the triangle is different from the definition for the cube. However, I can declare that every, every derived class that is inheriting from this interface must have a definition for a particular method. So here I can see that there should always be dull blue get area. Alright? So anything inheriting from IS shape. Most implement double get area. This is why we call it a declaration or some, some languages would call this like a function prototypes. So this is just seeing that this is the datatype, this is the name. Maybe there are parameters, but that's all there is to it. It's not a definition and it's not a function call, it's a prototype. Know, I can let everybody inherited from a sheep. Know. You're going to see WE inheritance one, you cannot inherit from more than one classes at a time. However, you can inherit from a class and an interface or multiple interfaces at that time. Those are the rules right here. I can tell. Jaws triangle. Yes, you're inheriting from shape. And let's see. None of them have get era defined. Let me leave get era in queue. Triangle and a rectangle do not have get era defined. Now remember that the problem was that we shipped it told without the ability to calculate the area for rectangle. And no, I removed it for a triangle. Book cube is fine. Qb just needs to return height, a whole, Is it again? No, it's width versus length, sorry, length times width, The area of the cube. Alright, that's fine. But then these two don't have any method defined for that. I can actually just go up here to the inheritance side after the colon and see Como I wanted to inherit from i shape also, let me move. I shaped Switzerland file. Let me do that quickly. I notice that it's still just a CSS file and the name is I shape. And you always wanted to make sure that your filenames match the name of the class. It's in its own file, It's an inheritance, it's an interface rather should enforce the implementation of this, a method that is being prototypes are declared. When I go to the class that is no inheriting from my shape, I see an error. What is this area? It's seen that rectangle, which is the class, does not implement the interface member I seep dot get era. You see in that I need to make sure that if I'm inheriting from Isua, that I'm implementing what IS shaped said should be implemented. So I can just do Control dots and implement interface and it will put the method stub for me. This is a good way to enforce at the editing, the compiling level. That certain rules are being met. Every shape should be able to calculate its area. Rectangle should have get era by letting all of these inherited from i shape. I am no enforcing the rule because this program would never compile. I couldn't never ship it all in this state because it wouldn't work. I have to make sure that I am going to have our representation of getArea before I can move forward. No, this is just going to throw not implemented exception, which is another exception type, but that's fine. We can erase that. Then for rectangle, I can return length times width. All right, why do I have access the length? Because linked was defined in the abstract sheep and it's inheriting from that. So I can easily access them without needing to redefine and redeclare and put into many properties. Length times, what's its height? It was height and width. So that means I need to actually put in the property for, with fear. There are a lot of permutations as the whole this works. I mean, I'm not going to be able to cover all of the variations. I just wanted to give you guys examples of why you would have inheritance by a class versus inheritance by an interface versus both. Cube currently is not inheriting from any interface I can tell it to, but it already did the implementation, so that's fine. There's no error there. Like I said, with the inheritance margins, you can always jump between the class files and you can jump to the definition if you need to. You can see where it's being defined all over the place, etc. So here in triangle, if I tried to get area of a triangle, it would give me an aerosol here. I can have the definition inside the triangle class, half B. So that's 0.5 times the base, which I went to use as length. That's half base times height, right? Sorry, it's been awhile begin to let's just say that's half base times height, really and truly, right? And that is what the triangle area is defined as. This is the rectangle area. And then the cube area is that even though you're inheriting, you can have your own methods here because I can easily see public double get volume. And the volume of the cube would be length times o. I said length times length here, length times width. Length times width times height. All right? Yes, I'm inheriting 11 is begin forests, but I can have my own and my own properties even though I mean, inheriting, inheritance helps us to reduce repetition. And remember, DRY principle, don't repeat yourself wherever you see opportunities like this, where you might be repeating certain properties across multiple classes, still flat that you want to put them in a base class and do inheritance to cut down all of that repetition. Let's write a quick program know just to put all of that to the test. So I have the cube already and I'm going to show you the var keyword. And also var is a quick way to define a variable or an object. The thing with var is that it will assume it's type based on what is on the right-hand side of this decoration. So when I say var triangle, it doesn't know what data type it is until I tell it it's a new triangle. If I said var rectangle, then the object call, the object is called triangle. What is still just going to be of type or tongue glucose? That's a type I defined. This is a common it, you'll see what C-sharp development where instead of seeing string name and an age and so on. But I was strict on that earlier because I wanted us to appreciate the data types. Over going forward, you will see me using var, a bit more. Var triangle. I can say var cube. I can say var rectangle. Rectangle is equal to a new object off rectangle, etcetera. Then I'm going to do some console, right lines. You can hit pause and replicate those but the three objects, and then I have three. Little variables here. I'm just defining them as int, but like I said, equal to easily just see far. Just by seeing virus with no, That link is supposed to be integer because on the right-hand side, we're seeing we're sending over an integer. That can be a double-edged sword because it's not willing to give you an error if the datatype isn't what you expect. However, when you are strict like this, you can see from a mile away that you might be writing incorrect code for the situation at hand, like here. I tend to favor using the primitive datatypes when I need to. But for the more complex ones, I will rely on fire, but sometimes once again, you can use them interchangeably. Here I'm just prompting for the length, the width, and the height. Then I'm going to set cube dots. Length to be equal to length, cube width to be equal to the width value coming in. Cuba, dot height to be height. Another the same for the triangle with length, triangle with width and triangle with height. Notice that this one is giving me an error because triangle does not have a width property defined in it. So that was Visual Studio's suggestions. I'll remove it. That's fine. And then rectangle is going to be taking length and width, whatnot tight. Know, there are different ways to define our assign these values. This is one way to do it. There's another way to do it. There are at least two other ways that he could be done more efficiently. In the next lesson, when we were looking at constructors, I'm going to show you that after we have all of these defined, we can easily do some console dot write lines. I'll just borrow one-off these and see triangle. Let me start with cube, cube area. Then we call cube dots, gets area. Usually that is after we assign the values, we have a definition for it gets era there and q would also have get volume. So I'll just call that at the same time. Then we'll just do the triangle. Here is called the triangle gets era method. And we can do the same thing for the rectangle area. All right. I'm just showing you that when you start getting the hang of how everything works, everything flows. You will see that object oriented programming is there to make your life easier. So look how much code we've written. Leuko minute things we've done yet, or program.cs is so simple, it's just defining three objects, getting data and then sending it over and then the process to get all of those values, those are hidden from us. When I test this out, I'm just going to use the same three values obviously for all three shapes. The cm length to see him within the seam. All right, So let me free up my console. So let's say length is 50 by 40 by 32. And then the area of the cube is 2 thousand, but the volume that should have been volume is 2032. And then the triangular areas. So this one I'm not sure if that's right. Yes, I knew he was incorrect because I said plus instead of asterisk, apologies. But I hope you see the value of inheritance in this context. Once again, through inheritance, I was able to one creates a base class, that's I call it an abstract class called shape, that define certain shared properties that all shapes have. And then I could let every other shape just derive or inherit from that BCE shaped gas. I also looked at using inheritance to enforce that a certain method or a certain myths thoughts, because you're not limited to just one. But certain methods were enforced in the shape. So here I think of alleviated some naming convention. So control data and it should be Gettier with a capital G. Same thing for it to get volume. So it wouldn't throw incarcerated for me. What I was saying is that the, the interface when inherited acts like a contract, a contract states that you are obligated to do this thing. Once you're inheriting from this contract, he means you're already good to carry out the operation defined by the contract. That's basically, oh, whoa, inheritance interfaces work. And he didn't get far more complicated than this. But when you get to bigger applications, then you will start seeing it. But this is a nice quick introduction to inheritance with classes and interfaces. 26. Constructors: All right guys, In this lesson we're looking at constructors. So I'm going to reuse the inheritance project only because it already has so much coordinate and I think it's a perfect way to show what constructors are and hold their useful. When we're going through inheritance had mentioned that there are easier ways, quote-unquote, to assign values to newly created objects. One such way would be to, and I'm going to just rearrange the code little tear someone to move the object definitions to below, where we asked for the values. When I am defining cube, similar to when we were doing the IRAs, when we could say give me a new area and then put in the values at the same time. I can actually do that with a brand new class. I can actually say, give me a new cube, open and close curly braces. And then I can start assigning the different values to the different properties, right? So I can see a width. You should get the value of ten. Since I got it through user input of whatever k-mean toward local variable. All right. You get the length of whatever came in through our local variable. Height gets the same treatment. Alright? That is, this one line of code would actually eliminate all these three. Sit at. This one line would be seeing given me a new cube that is defined to have the width according to what came in, length and height according to what came in, as opposed to me going cubed dot length is equal to length cubed dot width. It works. But once again, I'm showing you alternatives. I can actually remove those three lines of code. I can do the same thing for the triangle. And I would actually not running into the same issue when I was doing the triangle that accidentally put in width. And I didn't ask where our hypotenuse for my triangle. You see that? That's fine. Height is equal to height Como, and then length is equal to length Como. Then I could easily put in our hypotenuse value. I didn't ask for one, so I'm just going to hard code it to ten. So that eliminates those two lines of code. And then I can replicate that with the rectangle instead of typing in from scratch, I'll just borrow the code from the cube and remove the height, in fact, I believe is the one that I don't need for the rectangle, which eliminates those two lines of code. Look at that much neater. No, that's not what constructors are. Working my way up to showing you what constructors are. Constructors are default methods that are going to be created in a class that enforce that an object must meet the specific occasions before it can be instantiated. That's a mouthful. Let me explain. No, there is a default constructor that takes no parameters. So that's why we can just see cube is equal to a new instance of cube, whether or not we provided values. Because remember it worked, you worked earlier when I created the new cube without any values there. So it was just an object with no height, width, or length. That would have been 0. However, if I wanted to enforce that, in order to create a cube, you have to provide those values from the get-go. Then I would enlist the help of a constructor. To create a constructor. I'm just going to press Shift 121 cube and jump over to the definition. In force out constructor, you can easily write the keyword CTOs and then press Tab twice, and then that generates this method stop. Node. Constructors are characterized by the fact that one they're public and the tool, they have the same name as the class. Three day take r can take parameters. Default constructor is one that doesn't need parameters without me actually doing that, there was a default, it's implied, which is why I was able to get away with cube with no parameters. That's the default one that is already implied. But sometimes you would find people that are very explicit with the default one, especially when they have an alternative one that is not the default one. You can actually have constructor overloads the same weekend method overloads. I can define another constructor, CTR top tab. And then I can say no, you see it's complaining because it's seeing two constructors that are identical. It's seen these already one here with the sea environment that types, that's fine. But what if I wanted to enforce that in order to create a cube? You have to give me width. You have to give me a height. And you have to keep on splitting height wrong. And then you have to give me what's the other one? Breadth and length. There we go. You have to give me these three values. And once you give me those three values, I can easily instantiates the properties to those values. That we can't have a cube that has no sides and think about it. Have you ever seen ICU with 0 length, 0 within 0 height? Maybe you have, it's called an invisible cube. In order to create a cube, you must give me the height, the width, and the length of the cube. So I can actually remove this default constructor and have only one constructor, which is seeing, I need these three. No, when I do this, look at what happens in the program.cs, there's no way I can define an object of cube widow passing in those values inside of the parameter listing. So even though this does not appease the compiler, right? So let me remove that and show you that in order to create a cube. If you hover over it, it's going to show you that you have to have the int width in tight and length. So I'm going to have to provide the width. And I'll do that with the user provided value, the height and the length. No, it is satisfied. So now it has that cube. When you say, give me a new cube and you say give me nu cube, you have to provide the width, the height, and the length. Once you do that, all the values are going to be assigned. Because in the constructor I said once you get those automatic idea scientists, this new object of a cube already knows what its width is, what its height is, and what it's meant is upfront. I don't have to tell it afterwards like this, our whole we had the code initially. All right, triangle can still get away because I didn't define in the constructor. So even if I give it the default constructor, it will still work. But let us say I gave it both. Both the default and one that says give me the width, sorry, not with the length, the height, and the hypotenuse. Or they'll say hype, right? Or I could enforce that. I only want the hypotenuse. It's up to me what is the default value? What is the bare minimum that this object must have in order to be instantiated. If I have two constructors like this, then what happens is that I can easily define a default one like this and assign the values later on. Or I can have another one where I can pass in the values. So let us see I'm going to use the other one node. So if I say triangle open parentheses, then you will see that it's showing me that I have two options to create a triangle. I can created blank, or I can put in the hypotenuse value. And let's put in ten, or I put in user input, whatever it is. That's all that is required of me. Know I have triangle using the default constructor. Let me do it in triplicate. So you have the default constructor. This is completely empty. No height, no with no length, which is not really practical. Then you have the one where yes, I created it, empty boats, I'm assigning the values. And then I have one where nothing else has any values except the hypotenuse. All right? So all of those things are options when it comes to putting in constructor. So you can have multiple constructors. So lots of times when we're defining new classes, even C-sharp built-in classes, you might find that you can define an object. Sorry, when we're defining objects off glasses, you can define the objects with parameters, sometimes with all parameters. These are just overloads off constructors that exist in the class. If I create one constructor, that is my base constructor. If I create multiple constructors, then those are all options because I could easily just expand this and say give me the hypotenuse, the height, and the length. If you want. You have that option also if you're creating a triangle, if you can't do it blank, you can give me just a button user, you can give me all three. What am I going to do when I get the values in each settings? So when I get the hypotenuse alone, I would say that hypotenuse here, new values. Keep. If I get to all three, then hypotenuse your new value is heap. Sure. When I get the height, its height, and when I get the length, its length, then all of my definitions can be characterized by all of those options, right? So triangle three could use the Option, option overload s1, we're just passing the hypotenuse is one where I pass in hypotenuse and let's use ten. I pass in the height, and I pass in the length. Three different ways to instantiate a triangle object. Of course, each one is going to have a different outcome because this in its current state when I tried to get area down here. Sure. I'm just going to get 0 because there is nothing I signed. However, getting ear from this one would give me a bitter value. Let's try that with Triangle Tool and then try it with travel, the one where we only have that button use, that's probably going to give me 0 also cause that's half times 0 times ten, which is 0. And then this one where I'm providing all the values should give me yet another outcome. So let's say that for a spin, All right, so entering some random values. And then we see here that we have two zeros. The first 0 for the triangle here is because it was empty, those empty objects. The second one is triangle to where it got the height, the length, and the hypotenuse hard-coded as tin, which of course could easily have been user inputs. Then we have the third one which is 0 because well, we only got the hypotenuse nor height and width. So the half base or half-length times ten is going to give us half times 0 times ten, which is 20. Then the triangular area for the third one where it got ten to height and the width is going to be 270. Alright? So that's pretty much, That's pretty much it for hole you use constructors, right? So once again, constructors are there to enforce the requirements for a certain properties before you can move forward with the instantiation of an object. 27. Create GitHub Account: Let's look at creating a GitHub account. If you don't have one of these, then you can get one in maybe five or fewer minutes. Step number one, go to github.com, that's GIT HUB.com. Step to go ahead and give them your e-mail address to sign up? No, I already have an account. I can actually login to my account and show you what it looks like. That's what it is. It's almost like a social media platform, but for developers and open source contributors, and the more followers you have is the more activity you will have on your screen. The more repositories or projects that you add, the more you have here. So it's very advantageous for keeping backups of your source code, for referencing other person's source code. And in general, collaborating when working in teams. So go ahead and create your account, and once you do that, you can move on to the next step. Like I said, it is a very simple procedure. You give them an email address. I'm going to try and give them one that I don't think they have for me yet. And then once you do that, you just go ahead and fill out the rest of the form, enter the e-mail content and give them a password. And I think after this they send the verification code and you check that. And then boom, you have an account. Once you do all of that, you're ready to move on to the next lesson. 28. Add Solution To Source Control: All right guys. We are at a very good milestone. We have done a lot since we started this course up onto know. We have a number of projects and a number of code references and exercises. And I think it has been a wonderful journey thus far. This juncture I wanted to introduce to you the concept of source control, and it's a very simple concept to grasp. Firstly, you'll need your GitHub account, and I'm sure you've already created one of those from Visual Studio. It is very easy to integrate with your GitHub account. The first step here, and I'm just going to close all windows, all bits of code. I can just right-click and say all tubs goes on TBS. So we have a blank window. From here. If you look at the bottom right-hand corner, you'll see a blended as his ad to source control. And you click it, it will say get. If it does not see that, then you may need to revisit the installation of your Visual Studio. So when you click Get, it will actually launch this little window that is suggesting that you create a Git repository. You may also ask you to authenticate against your GitHub or cones at this point. So here you have two options. You have GitHub and Azure DevOps, both our Microsoft owned, both our variable for both of them are source control engines that are supported, are support that gets protocol. Either one works. However, I'm going to show you with GitHub as it is the most recognized open source platform. And he told us you to publish your code and have a portfolio to show others that this is what you've written, this is what you'd know. Proceeding with GitHub, you can just go ahead and fill in off-course, you're authenticated so it would fill in certain blanks for you. Then he would see a repository name and then you can give it some more texts. C-sharp with net six, I went to see console programming with knit six. And he can give it a description. Activities surrounding the B6 of c-sharp programming in dotnet seeks. Know. You may be wondering, okay, why do I want to publish my code? I have it on my computer. Well, one source control helps you to manage changes. So we did a lot of changes. We weren't trucking with source control. So I'm sure if I asked you to recall and our undo some of the things from the earlier lessons, it would be very difficult. So that is a benefit because if you make a mistake to what was working and you're not sure how to fix it. You can always go back to Source Control, get the version that was working and then start over. So it's good, it's beneficial for that reason. Another benefit, once again, is that it helps you to share code not only with potential employers or your friends, but also with your team. If you're working on a project and all of you have to be contributing instead of copying and pasting, I'm trying to zoom session. You can actually just use source control and centralize where the code is stored, which will be on GitHub. And then everybody would like subscribe to that repository and be able to see everybody else's changes, make changes, and everybody can be on the same footing when he comes to leveling up diversion or contributing to the application. I'm going to untick private repository because I don't want this to be private if you want to hide your application from the public than you choose private, otherwise you untick that. And then you can just say Create and push. Once you've done that successfully and noble things will change in Visual Studio one, you will no longer see the button that says Add to source control. And I just wanted to show you master. I just wanted to show you this. It'll get symbol with the name of the project or other projects. You can see I have a number of projects on Source Control. You'll also see some blue padlocks appearing beside your files. Those mean that they are checked in there? No. I have the same level as what is centrally hosted. If I'm to go to my GitHub profile, I would be able to browse through my repositories. Let me start from scratch. So this is my GitHub homepage and to the left are my Repositories. I can see console programming within that seeks and it will filter and show me the project and all the files saw off the project files that I uploaded are here for public access because I made it public. If I wanted to change, it's a private. I go to settings and I scroll down and I see change visibility, then that would allow me to change it to private. I could also archive transferred to somebody else or just delete it if I really didn't want to anymore. I can also rename. So as long as you don't clash with names, then that's no problem. If I wanted to add persons to this repository, meaning by my teammates, persons I'm coding with for free, you can add up to, I think, about five collaborators. So you just have to confirm your password and then you'll be able to add people. All right, so I can go ahead and say, eyed people search for the username, send them an invitation. Once they see that invitation, they can accept and they will have access to the repository where they can come and close knit or open it with Visual Studio by clicking code on their own computer. They can say Open With Visual Studio, which will then allow them to open the project locally in a new Visual Studio window at a location of their preference. So if I changed this path to testing, alright, now I can clone it and it will get to, it will automatically download all of those files and set them up for me on my computer. This is what your teammates would be doing after you created the project, your team, it would go ahead and clone and then they will be able to open the solution file console programming SON. And then they would be able to interact with all of the project files accordingly. Now, when I change his me to a file, let's say the Hello World, this was very simple. And then maybe I made that change. Whatever the change is, it could be new text, it could be a space, whatever it is, you'll see that this now has a red tick. This red signal means that I have modified the file since the last time. So this is going to be a test modification. That's my modification. I have modified the file relative to the last version that was on GitHub. After I've done my change, we're working as a team, no one. It was my opportunity to know to modify this particular parts of the program and I've done it and I'm satisfied. I need to check it in to GitHub so that everybody else can have access to the change. I would have to go to a window called the good changes. You can get to there by going to View and seeing changes will actually hide it earlier. But it was Datsun when students to dock it to the side here alongside Solution Explorer. There we go. I'm not sure why not going to get fixated on that. Get changes. That's what I'm focusing on. So get changes, one, you put in a message, what did you modify it? I would give a nice message, modified the Hello World program. Then I can see commit all and seeing, so click that little caret besides comments All and click Commit All and sync. And what this will do is push that change to GitHub. So no, all I did was a few button clicks. Now the padlock is back. And if anybody else goes back to GitHub, notice all of these project files when I refresh, it's going to show them it at 20 seconds ago there was a change. And it's going to show me which project was changed and what the message was. If I click on that message, modified program, you see here that it's showing me that it added two new species as well as what's in red is what was what's in green is what note is. All right. That's why I said he can track changes because now you can see exactly who made that change. So somebody who destroyed the application, you know who to blame. Alright, you can easily truck all the changes that have occurred on each file with each iteration. And you have all of the versions that he can go back to seek and click on the commits. Then you can see based on the messages, who did what and what the message was, you can always go back to that version of the code and retrieve that one. All right, so this is good for if somebody in the team destroys the code or even you destroy the code and you wanted to revert, it's easy to just scroll back to that, a cleaner version. The flip side for the team members who are waiting on the updates. So this is the original Visual Studio window. And if you look at my program.cs, it does not have that update, right? So let us say no, I made the updates and, you know, needs to retrieve the latest code for that update onto your application, onto your machine. All you have to do is go to get changes. When that window comes up, let me fix the docking once again. When get changes comes up, you just need to do a pool cycle. I'll give you a call and say, Hey, you know, I finished the work and I checked it in, get later. So you're like, Okay, thank you. And then you just come to get changes and then you do a pool. And then it will go up to GitHub, get all the changes, and then look at that. It just automatically updated my file for me. That is why GitHub is perfect for team situations and not just github bought using a source control management system. Github is just one of your options. You have other options are there get is one of the protocols. But I'll be the most popular. And the one that I would recommend GitHub is one of the most popular platforms, easiest to get started within my book, and also one that I recommend.