C# is an object-oriented programming language created by Microsoft that runs on the .NET Framework. C# has roots from the C family, and the language is close to other popular languages like C++ and Java. The first version was released in year 2002. The latest version, C# 12, was released in November 2023.
C# is used for:
The easiest way to get started with C# is to use an IDE. An IDE (Integrated Development Environment) is used to edit and compile code. Applications written in C# use the .NET Framework, so it makes sense to use Visual Studio, as the program, the framework, and the language, are all created by Microsoft.
Comments can be used to explain C# code, and to make it more readable. It can also be used to prevent execution when testing alternative code.
Single-line comments start with two forward slashes (//). Any text between // and the end of the line is ignored by C# (will not be executed).
This example uses a single-line comment before a line of code:
// This is a comment
Console.WriteLine("Hello World!");
This example uses a single-line comment at the end of a line of code:
Console.WriteLine("Hello World!"); // This is a comment
Multi-line comments start with /* and ends with */.
Any text between /* and */ will be ignored by C#.
This example uses a multi-line comment (a comment block) to explain the code:
/* The code below will print the words Hello World
to the screen, and it is amazing */
Console.WriteLine("Hello World!");
Variables are containers for storing data values. In C#, there are different types of variables (defined with different keywords), for example:
To create a variable, you must specify the type and assign it a value:
type variableName = value;
Where type is a C# type (such as int or string), and variableName is the name of the variable (such as x or name). The equal sign is used to assign values to the variable.
To create a variable that should store text, look at the following example:
string name = "John";
Console.WriteLine(name);
You have already learned that Console.WriteLine() is used to output (print) values. Now we will use Console.ReadLine() to get user input.
In the following example, the user can input his or hers username, which is stored in the variable userName. Then we print the value of userName:
// Type your username and press enter
Console.WriteLine("Enter username:");
// Create a string variable and get user input from the keyboard and store it in the variable
string userName = Console.ReadLine();
// Print the value of the variable (userName), which will display the input value
Console.WriteLine("Username is: " + userName);
Strings are used for storing text.
A string variable contains a collection of characters surrounded by double quotes:
string greeting = "Hello";
A string variable can contain many words, if you want:
string greeting2 = "Nice to meet you!";
A string in C# is actually an object, which contain properties and methods that can perform certain operations on strings. For example, the length of a string can be found with the Length property:
string txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
Console.WriteLine("The length of the txt string is: " + txt.Length);
There are many string methods available, for example ToUpper() and ToLower(), which returns a copy of the string converted to uppercase or lowercase:
string txt = "Hello World";
Console.WriteLine(txt.ToUpper()); // Outputs "HELLO WORLD"
Console.WriteLine(txt.ToLower()); // Outputs "hello world"
Very often, in programming, you will need a data type that can only have one of two values, like:
For this, C# has a bool data type, which can take the values true or false.
A boolean type is declared with the bool keyword and can only take the values true or false:
bool isCSharpFun = true;
bool isFishTasty = false;
Console.WriteLine(isCSharpFun); // Outputs True
Console.WriteLine(isFishTasty); // Outputs False
C# supports the usual logical conditions from mathematics:
You can use these conditions to perform different actions for different decisions.
C# has the following conditional statements:
Use the if statement to specify a block of C# code to be executed if a condition is True.
if (condition)
{
// block of code to be executed if the condition is True
}
In the example below, we test two values to find out if 20 is greater than 18. If the condition is True, print some text:
if (20 > 18)
{
Console.WriteLine("20 is greater than 18");
}
Loops can execute a block of code as long as a specified condition is reached. Loops are handy because they save time, reduce errors, and they make code more readable.
The while loop loops through a block of code as long as a specified condition is True:
while (condition)
{
// code block to be executed
}
In the example below, the code in the loop will run, over and over again, as long as a variable (i) is less than 5:
int i = 0;
while (i < 5)
{
Console.WriteLine(i);
i++;
}