C# Program and Syntax

In previous chapter, we created a C# file called Program.cs to print "Hello World" to the screen, the Program.cs is like:


using  System;

namespace HelloWorld
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            Console.ReadKey();
        }
    }
}

Once above code is compiled and executed, it will produce the following result:


Hello World

Now lets go through each and every word in this program -

The first line of the program using System; - the using keyword is used to include the System namespace in the program. A program generally has multiple using statements.

The next line has the namespace declaration. A namespace is a collection of classes. The Program namespace contains the class HelloWorld.

The next line has a class declaration, the class HelloWorld contains the data and method definitions that your program uses. Classes generally contain multiple methods. Methods define the behavior of the class. However, the HelloWorld class has only one method Main.

The next line defines the Main method, which is the entry point for all C# programs. The Main method states what the class does when executed.

The Main method specifies its behavior with the statement Console.WriteLine("Hello World");

WriteLine is a method of the Console class defined in the System namespace. This statement causes the message "Hello, World!" to be displayed on the screen.

The last line Console.ReadKey() is for the VS.NET Users. This makes the program wait for a key press and it prevents the screen from running and closing quickly when the program is launched from Visual Studio .NET.

Note:
1. C# is case sensitive language(means myClass and myclass has different meanings).

2. All C# lines ends with semicolon (;)

3. namespace is like a container which is used to organize the code.