Hi! Thank you for taking my C# tutorial for beginners. Let me quickly give you an overview of what you’re going to learn and how I’ve structured this tutorial. In the first section, I’m going to talk about fundamentals of C# and .NET.
one of the questions that a lot of beginners ask is what is the difference between C# and .NET so I’m going to cover that I’m also going to talk about CLR assemblies namespaces IL code and stuff like that then over the next two sections I’m going to talk about types I’m going to talk about primitive and non primitive types now at this point you still cannot write any C# programs but I have designed a number of quizzes to help you reinforce what you’re going to learn then from Section four where I talk about control flow you’re going to start writing simple C# programs and from that section onwards in every section you’re going to learn something new about C# and you’re going to write more interesting programs and finally I’m going to conclude this course with a section on debugging so I’m going to show you some of the tools we have so when you have bugs in your code you know how to find them and get rid of them I’m also going to talk about some good program practices that help you write better and more reliable code so we have a lot to cover and let’s get started okay so this is the very first section of this course in this section I’m going to start by teaching you the very basics of C# one of the questions that a lot of beginners ask is what is the difference between C# and net so that’s the first thing I’m going to answer here next I’m going to talk about CLR or common language runtime which is the runtime environment for .NET applications next I’m going to talk about the architecture of .NET applications and as part of this I’m going to introduce you to concepts such as classes namespaces and assemblies and finally I will show you all these concepts in action I’m going to introduce you to the very basics of visual studio and write a very simple C# application so you can see classes namespaces and methods in action I hope you enjoyed this section and let’s get started okay what is darknet framework and how is it different from C# some developers who are absolutely new to C# don’t know the difference so in this lecture I’m going to talk a little bit about C# and .NET framework C# is a programming language .
NET is a framework for building applications on the windows .NET framework is not limited to C# there are different languages that can target that framework and build applications using that framework examples are F sharp or vb.net okay now but what exactly is .NET framework Dartmouth framework consists of two components one is called CLR or common language runtime and the other is a class library for building applications in the next lecture we’ll talk about CLR in more detail okay before we understand what CLR is and why we need it let me explain a little bit about the history of C# before C# we had two languages in the C family the C language and C++ with either of these languages when we compiled our application the compiler translated our code into the native code for the machine on which it was running which means if I wrote an application in C++ on a Windows machine with 8086 processor architecture the compiler would translate my code into the native code for that machine that is a Windows machine with an 8086 processor now we only have different hardware’s and we have different operating systems so if I took the application that compile the application on the computer with a different architecture that would not run so when Microsoft was designing the C# language and the .NET framework they came up with an idea that they borrowed from the Java community in Java when you compile your code it’s not translated directly into the machine code it’s translated into an intermediate language called bytecode and we have the exact same concept in C# so when you compile your C# code the result is what we call IL or intermediate language code is independent of the computer on which it’s running now we need something that would translate that il code into the native code or the machine that is running the application and that is the job of CLR or common language runtime so CLR is essentially an application that is sitting in the memory whose job is to translate the il code into the machine code and this process is called just-in-time compilation or JIT so with this architecture you can write an application in C# and you don’t have to worry about compiling that into the native code for different machines as long as a machine has CLR that can run your application okay now let’s learn about the architecture of .
NET applications at a very high level when you build an application with C# your application consists of building blocks called classes these classes collaborate with each other at runtime and as a result the application provides some functionality now what is a class a class is a container that has some data which is also called attributes and functions which is also called methods functions or methods have behavior they execute code they do things for us data represents the state of the application let me use an example think of a car the car has some attributes like its make its model its color these are the attributes of a car a car also has some functions we can start it or we can move it so you can think of a car as a class in a real world application we have tens hundreds or even thousands of classes each class responsible for a piece of functionality an example of that is classes that are responsible for getting the data from the user process the data and display something to the user now as the number of classes in an application grows we need a way to organize these classes that’s where we use a namespace so a namespace is a container for related classes for example in .NET framework we have namespaces each containing tens of related classes we have namespaces for working with data like databases we also have namespaces for working with graphics and images we have namespaces for working with security now in real world application as these namespaces grow we need a different way of partitioning an application and that’s where we use an assembly and assembly is a container for related namespaces physically it’s a file on the disk which can either be an executable or a DLL which stands for dynamically linked library so when you compile an application the compiler builds one or more assemblies depending on how you partition your code in the next lecture we’re going to write a very simple structure application and you’re going to see all these concepts in action okay in this video we’re going to have a quick tour of visual studio and build a very simple C# application so here I’ve got Visual Studio open let’s go to file new project okay in this dialogue on the left side we’ve got a section called templates and here you see the kind of applications we can build with C# so as you see in the list we can build desktop applications web applications apps for cloud mobile services workflows and various kind of things but in this course and the subsequent parts of this course we’re just going to focus on console applications a console application is a very simple application that does not have a graphical user interface and it’s a great learning tool for learning a new language so we’re not going to be distracted by various complexities of larger applications so on the left side select windows and on the right side select console application then give a name to your project so let’s call it hello world which is a common tradition when learning a new language and specify a location you can put it wherever you want I know this concept of solution in Visual Studio we have this concept of solution which can have one or more projects with a very simple application you have only one solution and one project but as your application grows you add more projects each responsible for something different but now we don’t have to worry about it now click OK alright let’s see what’s happening here some developers get a little bit intimidated the first time they open visual studio and that’s very enough because there are so many menus and panels here that is a bit confusing but let me tell you something 90% of the time you’re going to use only 10% of these or even less so don’t worry about all these menus here you don’t need to use all of them at all times 90% of the time all you need is the code editor here sometimes you need the solution Explorer in fact I personally hardly ever use solution Explorer because I do everything with my keyboard and if you watch my course double your coding speed you will see that everything is possible with keyboard so you don’t need these panels here you don’t need to grab your mouse and navigate around you don’t really need this stuff also none of the stuff on the toolbar are ever required don’t worry about it everything you can do with your keyboard alright now let’s take a look at this first to char program so we created a console application and on the right side you see the solution Explorer panel in case you don’t see that go to view and select solution Explorer top you see we have a solution which has only one project under that we’ve got the project called hello world look at these four items here properties expand that we have a file here called assembly info this is the identification or the assembly that will be produced as a result of compiling this application so when we compile the console application we’re going to get an executable and that’s an assembly that assembly has an identification look at these attributes here like the title description which is currently not set company product copyright trademark culture a grade you know various kind of things like even version so these are all part of assembly identification or assembly manifest in most cases you don’t have to worry about it but if you want to create an assembly and you want to distribute it send to other people then you may want to come here and give you the proper name and a proper version so for now we don’t have to worry about it on the references you see any assemblies that this project is referencing to do its job when you create a project with visual studio by default it as a reference to a bunch of assemblies that you’ll see here these are all part of .NET framework so at a minimum Visual Studio assumes you’re going to use classes in system assembly or system the data to work with databases and so on you may not necessarily use all these assemblies in your project but that’s just part of the template config’ is an XML where we store the configuration for this application sometimes you may want to store connection strings to the database or you may want to have some settings about your application all of them will end up here and finally you see program dot C s which is where we are going to start writing code all right let’s see what’s happening here so in this file program that C S on the top you see a bunch of using statements what is this all about well our project is called hello world so by default Visual Studio creates a namespace called hello world when we write code in this namespace we have access to any classes defined in this namespace so if you want to use a class that is defined in a different namespace we need to import it in our code file and that’s why we use the using statement so by default Visual Studio as these five using statements system is a namespace in .NET framework and that’s where we have all these basic utility classes and primitive types there system that collections that generic is used to work with lists collections and so on system that link is used to work with data and it’s a comprehensive topic that I have covered in my C# Advanced Course system the text is used to work with tags and coding and stuff like that and finally system the threading is used to build multi-threaded applications in this video we’re going to create a very simple application and we’re not going to use any of these for namespaces here so we’re just going to use system for now I’ll leave them there and then I will show you how to clean them up all right so here’s our namespace and insight namespace by default we have a class called program so every console application you create with Visual Studio has a class called program inside program by default we have a method or a function called main and that’s the entry point to the application so when you run your application CLR execute the code inside main method and that’s where everything kicks off this method is declared as static and that’s something I’m going to cover later in the next section methods have input and output so what goes inside parenthesis is the input to the method which we call parameter or argument note that parameters are optional but in this case in the default template the main method has a parameter called args which is of type string array we’re going to learn about string array in the next section what you see before the method name is the return type or the output of the method void in C# means nothing that means this method does not return any value it just contains some code that’s it also note that C# is a case sensitive language so this main has to be with capital M otherwise CLR is not going to find this method as the entry point of the application okay and one last thing is note these curly braces so where we have a block of code we need to surround it with curly braces so that is applicable for methods for classes and for namespaces alright now let’s write a very simple C# program so let’s go here we have a class called console which is used to read data from console or write data to it it has a bunch of methods access this method using the dot notation and here you see various members of this class methods are indicated by a purple cube so beep is used to play a beep sound or clear is used to clear the console we’re going to use the right line method this method can optionally take a parameter so I’m going to pass a string here hello world just that I note that statements in C# terminate with a semicolon as you see here now take a look at using system on the top do you see that it’s highlighted whereas the others are grayed out the reason for that is in this file we are using a class called console which is defined in the system namespace that’s why that using statement is active we are not using any classes defined in other namespaces and that’s why they’re grayed out so we can get rid of them to make our code cleaner we can either delete each one by ctrl X like that or if you’re using resharper you can get rid of all of them by pressing Alt + Enter here and selecting the first option which is remove unused directives in file so it’s faster now let’s run the application with ctrl + f5 so this window that you see here this black window is what we call console and that’s why this kind of project is called console application you okay that’s it for this lecture from this point in every lecture we’re going to learn something new about C# and we can write more interesting and more complex programs I hope you enjoyed this lecture and thank you for watching well hello it’s mush here your C# instructor I just wanted to quickly let you know that this video you’ve been watching is actually part of my C# basics course on udemy in this course I walk you through all the core concepts of C# in a step-by-step fashion plus you get access to exercises cheat sheets and a discussion board to ask your questions in case you’re interested you can get this course with a discount using the link in the video description and if not that’s perfectly fine continue watching as the next section is coming up okay this section is going to be the first step in your journey to learn C# so I’m going to introduce you to variables and constants I’m going to talk about various data types and type conversion I’m going to talk about scope and overflowing and finally I’m going to talk about various operators we have in C# so let’s get started okay we are going to start our journey by learning about variables and constants a variable is a name that we give to a storage location in memory where we can store a value any constant in an immutable value that is a value that we know at compile time and that value cannot change throughout the life of the application why do we use constants the reason for that is to create safety in our application imagine you’re creating an application that involves some mathematical computation around circles we have this number called P which is 3.14 and we use that to calculate the area of a circle that number should always be the same we don’t want to accidentally change that in our program if you accidently change that everything is going to blow up in terms of the results the program produces so we declare that number as a constant and this way we create safety in our application in C# to declare a variable we start with the type followed by an identifier and finally semicolon here ain’t represent integer which is a number between minus 2 billion and plus 2 billion later in this video I will show you all the primitive types that you need to know also note that C# is a case sensitive language which means in this case these two identifiers are different one has lowercase n and 1 has uppercase n when declaring a variable we can optionally assign it the value like what you see here you don’t have to but there is one thing you need to know about variables and that is you cannot use a variable unless you initialize it so let’s say if I declare this int number here and I decide to display it on the console my application will not become part I have to assign it a value before I can use it before I can read it I will show you that later when we jump to coding to declare constant we start with the keyword cunt next we have the datatype and an identifier and here we have to initialize it with some value we cannot define a constant without setting its value there are a few things you need to know about identifiers first one is that an identifier cannot start with a number so you cannot have an identifier like the one you see here instead you need to replace one with the word one so an identifier cannot include whitespace so you cannot have an identifier like first space name it has to be one word an identifier cannot be a reserved keyword like int that you saw earlier if you are desperate to use a word that coincidentally clashes with one of the C# keywords you can perfect that with the add sign and finally as a recommendation always use meaningful names for example avoid a name like f n instead use first name this way your code will be more readable or maintainable and cleaner and everybody will understand that in terms of naming convention here are three popular naming conventions that have been around in the C language family we’ve got camelcase Pascal case and Hungarian notation with camelcase as you see I have bolded here the first letter of the first word is lowercase and the first letter of every word after has to be uppercase with Pascal case the first letter of every word has to be uppercase with Hungarian notation we prefix the name of a variable with the datatype it uses so here str represents a string Hungarian notation is not used in C# and I have noticed programmers coming from C or C++ background use that in their code if you’re one of them I highly recommend you not to use Hungarian notation because C# developers are not used to that and they don’t like to see Hungarian notation in the code it makes your code look a little bit ugly so in C# to name your local variables use camel case so as you see here the first letter of the first word is lowercase and if we had more words here in the identifier the first letter of every word had to be uppercase four constants use Pascal case so here you see I’ve got a constant here constant integer and the first letter of every word is uppercase here is the list of most commonly used primitive types in C# in fact the actual list is slightly bigger than this but I deliberately decided not to include those data types because they’re hardly ever used in fact they are there for interoperability with other languages I personally over the past 12 years of me coding in C# I’ve hardly ever used them in fact never so I decided not to confuse you with too much details that you don’t need in the next slide I’ve got a link here in case you want to learn about the other primitive types so let’s take a look at the table here on the left side I have divided these datatypes into four categories integral numbers real numbers character and boolean this column shows the C# data times and these are C# keywords note that C# keywords are always lowercase each of these C# keywords or C sharp types maps to a type in .
NET framework which is displayed in this column so these types are part of the.net framework and when you compile your application the compiler internally would translate the C# keyword you use here two equivalent .NET type the third column here shows the number of bytes each data type uses and I have listed these data types from the smallest to the largest in each category so in the category of integral numbers you see byte is the smallest it takes only one byte whereas long is the largest and it takes 8 bytes the more bytes we have the more storage we have and we can store larger numbers you don’t really have to memorize the range of each data type but remember white can store a value between 0 to 255 short can store a value between minus 32,000 to plus 32,000 integer can store a value between minus 2 billion to Plus 2 billion and long is even bigger than that in terms of real numbers we have three data types float double and decimal float maps to the single type in that framework and it takes four bytes and as you see it can store a very large number double is twice as big so it uses eight bytes and decimal uses sixteen bytes the more precision you need the bigger data type you use we also have character which is represented by char keyword and it’s two bytes so characters in C# are unicode and finally we have bull which represents boolean which can be either true or false in case you want to learn more about the other data types that I told you they’re not really used you can simply go to Google and search for C# built-in types and the first page is the MSDN page that lists all the primitive types in C# and most of these data types are pretty straightforward but there is something tricky about real numbers in this table I have listed the data types we have for real numbers load double and decimal I’ve highlighted double because that’s the default data type used by a C# compiler when you’re using real numbers so if you want to declare a float you need to explicitly tell the compiler to treat the number you have as a float here is an example I’ve declared a float call it number as I need one point two here I have added the suffix F and that is to tell the compiler to trade this number as a float if I didn’t have this F here compiler would think one point two is a double because double is the default data type for real numbers and of course I cannot assign a double number into a float so the program would not compile same applies to decimals so if you want to declare a decimal you need to add the suffix M at the end of the number in C# we also have a few other types which are not considered primitive types and they are string array enum and class we’ll learn more about them throughout this course okay that’s it for this lecture in the next lecture we’re going to talk about the concept of overflowing I hope you enjoyed this lecture and thank you for watching okay now let’s talk about the concept of overflowing here I’ve declared a variable of type byte cut the number and assign it to 255 as I told you earlier in the slide 255 is the largest value you can store in a byte now in the next line I’m increasing the value of number by one and trying to store 256 in the number but if you compile the application and display number on the console you will see zero and this is what we call overflowing so we have exceeded the boundary of the byte data type in C# by default we don’t have overflow checking which means we can modify the value of a variable at runtime and if we go beyond the boundary of its underlying data type we will get overflow now sometimes this is not desirable in your application you want to stop overflowing if that’s the case you need to use the check keyword so here is how it works we have the checked keyword followed by curly braces which indicate the code block and inside that block we have the variable declaration and any kind of arithmetic operations with this code overflow will not happen at runtime instead an exception will be thrown and the program will crash unless you handle the exception the topic of exceptions is an advanced topic and I have covered it in my C# advanced course for now all I want you to know is that if you use the check keyword overflow will not happen and instead the program will throw an exception now do we really need that in reality honestly I have never ever ever came across this situation because if I was concerned that in this case my number variable would overflow I would just simply use the short data type instead of byte but I decided to include the concept of overflowing because I wanted my sous-chef course to be comprehensive so just be aware of that in case you hear about overflowing somewhere but you’re probably not going to use that in the real world in the next lecture we’re going to talk about the concept of scope okay let’s talk about the concept of scope what is the scope scope is where a variable or a constant as meaning and is accessible take a look at this block of code here as you know a block is indicated by curly braces here we have three blocks of code here’s one here is another and here is the last one inside the first block I’ve got a variable called a an a is accessible anywhere inside this block or any of these child blocks if I go out of this block and try to access a the program will not compile the same rule applies to other variables so let’s take a look at this block here B is meaningful anywhere inside this block or any of its children if I go outside this block and try to access B I’m going to get a compile time error okay I think that’s enough theory for now let’s open up visual studio and do some coding okay let’s start by declaring a variable of type byte and call it number now we want to display it on the console so as you remember from the last lecture we type console dot write line and put the variable here note that as I was typing console dot write line my resharper plugin automatically added this using statement on the top system is a namespace and console is a class that is defined in the system namespace so in order to use the console class we need that declaration here on the top if you’re not using resharper you have to go here and manually type using system semicolon okay now take a look at this number here it has a red underline and if we put the mouse cursor here it says local variable number might not be initialized before accessing if you remember from the slides I told you in C# before you can access a variable you need to set it you need to initialize it and that’s the reason here we have the red underline we cannot display the number on the console before initializing that so if I try to compile the application we’re going to get an error to compile an application you press ctrl shift + B and here is the error list use of unassigned local variable number we can solve this problem by initializing number like setting it to 2 for example and you see the red underline is gone we can compile again control-shift be build succeeded take a look here okay now we can run the application by pressing ctrl + f5 okay so we got two on the console now let’s extend this example and declare a few more variables define an integer int count equals 10 and a float float say total price equals 20 $95 now note this red underlined here let’s find out what’s happening here so I put the mouse cursor here it says cannot convert source type double to target type float if you remember from the slides I told you by default the sea-shore compiler traits real numbers like this one here as double whereas we are declaring a float so here we need to explicitly tell the C# compiler to treat this real number as a float and we can do that by appending an F at the end so the error is gone let’s take your character so char character equals a note that in C# we enclose characters by single quote like here we can also declare a string string is not one of the primitive types and have covered it in a separate lecture in this course but for now let me show you how to declare a string which is type string give it a name first name equals mosh note that with strings we enclose them in double quote so that’s one of the differences between strings and characters and finally let’s declare a bull bull is working equals true so with bulls we can either set them to true or false both true and false our keywords as you can see they’re indicated by the blue color here and they’re lowercase so everything you see here that is blue is a keyword like static void string class name space and all these data types here now let’s display these variables on the console so let me show you a trick instead of writing constant the right line we can do a shortcut this is what we call a code snippet so we type CW that is short for console.writeline and then press tab and Visual Studio automatically converts that to console the right line there are various code snippets that help you write code faster and I will try to point them out throughout this course so let’s display count now another one totalprice and note that i can just type t oh and here is what we call intellisense it’s visual studios auto completion mechanism you don’t have to type the full name of a type or a variable as long as the intellisense detects tab and is highlighted here like total price you can simply press tab and there you go visual studio automatically completes that for us let’s display the character same here I just press tab again I type only a few characters it can press tab or enter and finally is working we run the application by ctrl + f5 so we got all these values on the console okay now let me show you something else in C# we have a keyword called var which makes variable declarations easier for example here instead of explicitly specifying the datatype for each of these here I can simply type var and I let the C# compiler detect the datatype for this variable here so let me replace all of this with var okay now if we hover the mouse over the VAR keyword we can see the underlying data type in this case is system that boolean which is the data type which maps to C# pull keyword how about this one that’s a string and this one is a character and this one is system that single which maps to float in C# and in the case of count it’s in 32 which is integer and same for a number so the tricky thing here is by default C# treats integral numbers as integer and when you use the VAR keyword it assumes that it’s an integer if you really want to go for a byte then you have to explicitly specify it as byte here but tell you from experience it’s safe to use integer in most cases in fact if you look at the classes in the.net framework in most cases integer is the data type used for representing integral numbers okay I revert this back now I show you something else so let’s take a look at this one here so it’s a char which is a character I can put the mouse cursor here and press control and then click that opens the object browser window take a look here it’s object browser and it’s a way to look at the various classes in your project or in the.
net framework in this case because I did a ctrl click on the char or VAR keyword this is what we got here so char is highlighted in the object browser on the right side you see all the members of the chart type so these purple ones are functions or methods if you scroll down here you see two fields here min value and Max value we’ll explore them shortly and note that here is the Declaration of Char Char is a structure we will cover structures later in this course and note that it’s a member of system namespace it can click system and that shows the system namespace as well as all the types defined in the system namespace so these are part of the.net framework ok let’s close this for now let’s explore another example so I’m going to get rid of all the code here we can simply press control X on each line and that deletes all these lines here ok let’s do a console the right line so CW tab this time I pass a string here I specify two placeholders and finally supply a couple of arguments okay let’s see what’s going on here so here what we have is called a format string it’s a kind of string that can be used as some kind of template so at runtime what we have here indicated by curly braces and 0 as the argument will be replaced by the value we pass here so 0 represents the first argument after this format string and 1 represents the second argument after this format string in this case bited max value so let’s run this application we got 0 and 255 and that’s the range that you can store in a byte we can do the same with a float so CW tap a format string float mean value float Max value run the application so this is the range we can store with a float it’s a huge number that is displayed using the scientific notation okay now let’s take a look at constants so I get rid of these two lines here control X control X we define a constant with the Const keyword Const float P 3.14 and we have to put F at the end because it’s a float now because we declared P as a constant here I cannot change it in my program so I cannot go here and say P equals 1 the compiler is not happy and that’s why we see that red underline here if you hover the mouse here it says read only local constant cannot be used as an assignment target it’s a little weird expression to understand but basically the intention of using constants is to have some kind of safety in your program so if there are values that should not be changed throughout your program you define them as constant and this way you want to accidentally modify their values well if you made it this far you seem to be very enthusiastic about learning C# and I highly recommend you to take my C sharp basics course using the link in the video description this way you can learn all the core concepts in a structured way and you don’t have to waste time jumping from one free tutorial to another you can see that currently this course has over 5,000 students with over 400 five-star reviews plus it comes with a 30-day money-back guarantee so if you’re not satisfied you can ask udemy for a full refund within 30 days and you get all your money back no questions asked again you can get this course using the link in the video description I hope to see you in the course in this video I’m going to talk about various kinds of type conversion in C# we have implicit type conversion explicit type conversion which is also called casting and we also have conversion between non compatible types here is an example of implicit type conversion a blight as you know takes only one byte of memory and an integer takes four bytes so we can easily copy a byte to an integer what happens at runtime is let’s take a look at this slide so here’s the binary representation of our B variable here so one is represented as seven bits of zero and one bit of one when we copy a byte to an integer what the runtime does is it prefixes that value with a bunch of zeros to fill the four bytes there is no data loss in situations like that when the compiler is 100% sure that the types are compatible and no data loss will happen values can be converted to a different type implicitly here is another example of implicit type conversion so we have an integer set it to one and we copy that to a float again in this example no data loss will happen but let’s take a look at this one here we have declared an integer and we’re trying to copy that to a byte and integer is four bytes so when we convert that to a byte three bytes out of four bytes will be gone and there is a chance for data loss now data loss doesn’t always happen it only happens if the value restored in the integer is beyond the capacity of a byte in this example one can be stored in a byte so no data loss will happen but if we had let’s say 300 here we cannot store 300 in a byte so as a result of that conversion data will be lost when the compiler knows that there is a chance for data loss it doesn’t allow implicit type conversion and you need to explicitly tell the compiler that you’re aware of the data loss and you still want to go ahead with the conversion in situations like that what we do is we prefix the variable with the target type so here I’m trying to convert I to a byte this is what we call as casting here is another example so we have a float set to 1.0 and if we try to convert that to an integer the compiler would complain I will show you that later in the coding demo so we need to tell the compiler that we are aware of the data loss and we still want to convert F which is a float to an integer so we cast it like here sometimes we are working with types that are not compatible but you still need to convert them for example we might have a number represented as a string as you see here and we need to convert it to an integer in situations like that because string and int are not compatible they cannot use explicit casting so we need a different mechanism for converting a string to a number in situations like that we need to use the convert class or use the parse method so convert class is part of .NET framework and is defined in the system namespace of methods for converting various types to other types and they all start with two in this case we’re trying to convert s which is a string to an int 32 in 32 as you know is a .
NET framework type which maps to a sushar p– integer type remember a blight is one byte short is two bytes and integer is 4 bytes and long is eight bytes you probably know that each byte has 8 bits so an integer which has four bytes times eight bits ends up being 32 bits that’s why it’s called two in 32 and in 16 which represents 16 bits equals to short which is 2 bytes we also have this parse method here all the primitive types that I explained in the last lecture like integer long float boolean they all have this parse method and the parsh method takes a string and tries to convert that to the target type in this case an integer here are some of the methods that you can find in the convert class to byte which converts the given value to a byte 2 in 16 to convert the given value to a short 2 in 32 to convert the given value to an integer and to n64 to convert the given value to a long okay in a theory let’s jump into code and see all this concept in action okay let’s say implicit type conversion in action first I declare a bite call it B and set it to 1 now I declare an integer and set it to be again to recap a byte is only one byte and an integer is 4 bytes so we can copy b2i without data loss and as you see there is no compile time error here let’s put on the console so console dot write line and we pass I here note that as I typed consult the right line my resharper plugin automatically added this using system statement on the top again if you don’t have resharper you need to go manually add this statement here we run the application by ctrl + f5 so we got on the console now let’s reverse this and see what happens so I’m going to get rid of this code here control X control X control X first I declare an integer set it to one then I declare a byte and try to copy I to B we immediately got this red underline here if you hover the mouse here the tooltip says cannot convert source type int to target type byte sometimes this error might be in a different file which is not open in Visual Studio here so you may see the error when compiling the application let’s simulate that so I compile this application by ctrl shift and B which stands for build so here’s the error cannot implicitly convert type int to byte an explicit conversion exists are you missing a caste so now you understand the concept of implicit versus explicit type conversion so what we need to do here is to do a cast so we casted integer to a byte now in this case no data loss will happen because the value is small enough to be stored in one bite let’s put B on the console console by right line B we run the application so everything is good but let’s see what happens if we said I – let’s say thousand we cannot store the number thousand in a byte the maximum we can store in a byte is 255 so if you run the application now we got to 32 because some of the bits were lost and this is the reason that C# compiler knows that there is a chance for data loss and it enforces you to explicitly specify the cast sometimes you know that despite the differences in data types there is no chance of data loss like in the last example where I was set to 1 in those cases we can safely apply a cast okay now let’s take a look at non compatible types so let’s clean up this code I start by declaring a string let’s call it number and set it to one two three four recapping from the last lecture note that here I could declare this with the VAR keyword and since our compiler automatically detects that this is a string so number will be defined as a string and we can see that by hovering the mouse here it says system that string now let’s say we want to convert that to a number if I declare an integer like I I cannot cast that number to an integer because they’re not compatible let’s take a look at the error cannot cast expression of type string to type int so if you see that error that’s the time when you need to use the convert class so we type in convert dot take a look at this method here – bite – char – in 16 in 32 and many other methods here so let’s convert that to an integer which is int 32 and pass number as an argument here now let’s print out the I on the console run application so I is 1 2 3 4 all good but let’s see what happens if instead I declare this as a byte and here we need to use convert dot 2 byte and here we display B on the console a byte does not have enough storage to store the value of 1234 so when we run the application now the application crashed the cancel is here and here is the exception exception is Dartmouth frameworks error reporting mechanism it’s an advanced topic and I have covered it in detail in my C# Advanced Course but in this video I will briefly show you how to handle exceptions so here it says unhandled exception the type of exception is system that overflow exception which means we try to store a value that was too large or too small for a byte so each exception or error as a type in this case overflow exception and has a message value was either too large or too small for an unsigned byte sometimes the exception messages are friendly enough that are easy to understand sometimes they’re a little bit tricky and the best way to work out what is going wrong is to jump on Google and search for the error and there’s pretty much always a Stack Overflow page that explains that now let’s describe that let’s see how to handle the exception here happened during conversion of that string to bite what we need to do here is to wrap these few statements with a try-catch block let’s see how it works so I just typed try and press the enter and visual studio automatically generated this block for me again this is what we call a code snippet let me undo this I’ll show you one more time so try see this try here in the intellisense and this icon represents a code snippet so if I press enter or tab you automatically get this code block so what I’m going to do now is to move this code enter a try block and the catch block gets an exception by default visual studio as this throw here don’t worry about it just delete it again I will explain it in detail in my sushar Advanced Course for now let’s see what’s going on here so the code that you put inside the try block will be somehow monitored and if an exception happens this block will be executed this prevents your application from crashing the reason our application crashed earlier was because we did not handle the exception so if you don’t handle exception the exception will be propagated to the .NET runtime and that the run times mechanism is to stop your application and display the error here we can handle the exception and that would prevent the exception from being propagated to .NET runtime so instead we can display a friendly message to the user saying for example console.writeline the number could not be converted to a byte now let’s run the application again see we got the firmly message and the application didn’t crash so what I want you to take away from this lecture is this we’re class works pretty well in most cases but in cases where the source type cannot be converted to the target type there is a chance for exception and you need to be aware of that and what you need to do is to wrap this block of code with try-catch let’s take a look at one more example before we finish this lecture let’s remove this and instead – drink call it STR and set it to true we can use the convert class to convert that value to a boolean so bull P equals convert that to boolean and we pass that STR here again in this example string and bull are not compatible and that’s why we cannot use explicit casting so here we are using the convert class we can display B on the console application so the true string was successfully converted to a boolean value that’s pretty much it for this lecture before I finish I just need to emphasize something here that throughout this course during early lectures you may see me using some short variable names like P or STR here that’s purely for demonstration and keeping things simple and in building real-world applications we should really avoid naming our variables ABC STR it’s not really a good practice the only exception is when we get to loops which you will see later in this course in for loops we use counter variables and we call them I or J it’s a common convention now here we are just starting to learn C# and it’s really impossible for me to demonstrate building a real world application because you’re just covering their basics or alphabets I hope you enjoyed this lecture and thank you for watching okay we got two operators in C# we have five types of operators arithmetic comparison assignment logical and bitwise let’s take a closer look at each of these operators we use arithmetic operators in computations where we are working with numbers so as you see in this slide we have add subtract multiply divide and remainder of division we also have two arithmetic operators called increment and decrement which are a shortcut for adding one or subtracting one from a variable so a plus plus is equivalent to a equals any plus one now with this increment and decrement operator there are two ways you can apply them you can use them as a postfix so in this example a is 1 and when we apply the postfix increment operator first the value of a is assigned to B so B is going to be 1 and then a is incremented by 1 so in this example after the second line is executed a is going to be 2 and B is going to be 1 now let’s take a look at a different way of applying increment operator as a prefix so in this example in the second line first a is incremented by 1 and then it’s assigned to B so after the second line both a and B are going to be 2 so be aware of this difference ok next comparison operators so we got equal which is indicated by double equal sign not equal greater than greater than or equal to less than and less than or equal to now what I want you to pay attention to in this list is that the testing for equality is accomplished by double equal sign and that’s different from a single equal which is the assignment operator next assignment operators so the most commonly used is the one with a seen the equal sign so here we set a 2/1 pretty basic now look at the next four types of assignment operators addition assignment subtraction assignment multiplication assignment and division assignment let’s see how they work for example addition assignment a plus equal 3 means add 3 to a so it’s equivalent to writing a equals a plus 3 and the same rule applies to other 4 assignment operators logical operators are used in boolean expressions which are often used in conditional statements will get two conditional statements later in this course so a real-world example is where you have a condition and you want to make sure that condition and another condition both are true or maybe one of them is true so that’s where you use a logical operator in C# the logical end is indicated by double ampersand and the logical or is implemented by double vertical line we also have the not operator which is indicated by an exclamation mark and finally in here we’ve got the bitwise operators bitwise operators are often used in low-level programming like when working with windows api or in sockets or encryption explanation of these is beyond the scope of this course but if you are interested let me know and I write a blog post for you now what I want you to take away here is that the bitwise End is indicated by a single ampersand whereas the logical end which we use in conditional statements is indicated by double ampersand same for bitwise or and logical or so remember the difference ok enough theory let’s flip over to visual studio and see all these concepts in action okay let’s start with the arithmetic operators first so I define two variables a equals 10 B equals 3 let’s add them together and display the results in the console that’s pretty easy right run the application so the result is 13 now let’s take a look at division so I replace the ad operator with division you the result is three the interesting thing here is because both a and B are integers the result of the division ends up being an integer if you like a floating-point number as the result of the division you need to cast both these numbers to a float so like this now if you’re on the application the result is a floating-point number now let’s look at a more tricky example let’s say C’s 3 B’s 2 and a is 1 I want to show you the concept of operator precedence so if I type a plus B times C what do you expect the result to be from a mathematical perspective B should be multiplied by C first which means two times three equals six and then it should be added to one so the result should be seven let’s run the application so C# behaves exactly as what we expected so multiply or division operators have higher precedence than add or subtract if you’d like to change the precedence you can do so by using parentheses so in this case if you would like to have a and B added together first and then multiply it by C this is how we would achieve that in this case the result will be 9 there you go okay now let’s take a look at comparison operators so let’s get rid of C here and instead see if a is greater than B very simple example right the result is false so what I want you to know here is the result of the comparison expression is always a boolean value which is true or false we can test for equality so double equal sign in this case a is not equal to B so the result should be false now let’s see the not equal operator so simply have an exclamation mark here followed by an equal sign in this case because a is not equal to B the result should be true okay now let me show you a more tricky example what do you expect here well first this is the not operator which is applied on boolean values or boolean expressions in this case this is a boolean expression and as you saw earlier it was true because a is not equal to B so we apply the not operator to that and the result ends up being false let’s run the application so we got files here but this code is not easy to understand or easy to read because here we have two negatives one negative and two negative and for us humans to negative is hard to comprehend two negatives always equal to one positive so in your program if you end up in situations where you have two negatives make sure to always inverse them with one positive so in that case I can get rid of the first negative and convert the second negative to a positive like that and we will get the same result which is false now let’s take a look at logical operators so I create another variable here VAR c equals 3 I’m going to change that to C greater than B and C greater than a what do you expect here as the result well C is greater than B so the result of that expression is true also C is greater than a so the result of that expression is true as well and here we have the end operator so true and true equals to true let’s run the application there you go now let’s make a tiny change here so this time because we know C is not equal to a this expression evaluates to false true and false results in false let’s run the application so we got false now let’s see the effect of the or operator so I’m going to replace the end with or which is double vertical line in this case that is true or false the result ends up being true and of course we can apply not operator here as you saw earlier which changes the true to false now this expression doesn’t really look easy to understand it’s just purely for demonstration of how we can combine different operators and make up more complicated expressions okay that’s it for this lecture I hope you enjoyed it and thank you for watching okay so we got to comment a comment is text that we put in our code to improve its readability and maintainability in C# we have two ways to write comments if your comment is only a single line you can prefix the comment with double slash but if your comment is longer and it’s multiple lines you need to start it with slash star and then finish it with star slash this type of comment is more like the comments we used to write in C and C++ code these days it’s more conventional to write either single line or multi-line comments prefixing with double slash so in this example we can rewrite this multi-line comment with double slash style like this now as a rule of thumb keep your comments to minimum use comments only win required and that’s when explaining wise house constraints and things like that do not explain what the code is doing your code should be so clean and straightforward that it doesn’t need comment if a comment explains just what the code is doing is redundant and the problem with redundant comments is we change the code but not everyone is very consistent in changing the comments so after a while these comments become outdated and because they don’t get compiled like the code there is no way to validate them and after a while they become useless so again keep them to minimum and explain wise house and constraints that you had at the time you wrote the code so the next person who is reading your code knows the reason why you wrote the code that way in this section you learn that C# is a statically typed language which means once you ticular a variable you need to specify its type and that type cannot change during the lifetime of that variable you also learn about the primitive types in C# such as integer character boolean and so on now in the next section I’m going to introduce you to non primitive types in C# such as classes or structures arrays strings and in ohms so I’ll see you the next section
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