Open Visual Studio
In the toolbar, go to File → New Project
Select the Console Application project type
Open the file Program.cs in the Solution Explorer
Add the following code to Main():

public class Program
{
    public static void Main()
    {
        // Prints a message to the console.
        System.Console.WriteLine("Hello, World!");
				/* Wait for the user to press a key. This is a common
               way to prevent the console window from terminating
               and disappearing before the programmer can see the contents
               of the window, when the application is run via Start from within VS. */
        System.Console.ReadKey();
    }
}

In the toolbar, click Debug -> Start Debugging or hit F5 or ctrl + F5 (running without debugger) to run the program.

Explanation

class Program is a class declaration. The class Program contains the data and method definitions that your program uses. Classes generally contain multiple methods. Methods define the behavior of the class. However, the Program class has only one method: Main.
static void Main() defines the Main method, which is the entry point for all C# programs. The Main method states what the class does when executed. Only one Main method is allowed per class.
System.Console.WriteLine("Hello, world!"); method prints a given data (in this example, Hello, world!) as an output in the console window.
System.Console.ReadKey(), ensures that the program won’t close immediately after displaying the message. It does this by waiting for the user to press a key on the keyboard. Any key press from the user will terminate the program. The program terminates when it has finished the last line of code in the main() method.

Using the command line

To compile via command line use either MSBuild or csc.exe (the C# compiler), both part of the Microsoft Build Tools package.

To compile this example, run the following command in the same directory where HelloWorld.cs is located:

%WINDIR%\\Microsoft.NET\\Framework64\\v4.0.30319\\csc.exe HelloWorld.cs

It can also be possible that you have two main methods inside one application. In this case, you have to tell the compiler which main method to execute by typing the following command in the console.(suppose Class ClassA also has a main method in the same HelloWorld.cs file in HelloWorld namespace)

%WINDIR%\\Microsoft.NET\\Framework64\\v4.0.30319\\csc.exe HelloWorld.cs /main:HelloWorld.ClassA

where HelloWorld is namespace