C Sharp for Beginners/Hello World

Here is your first C# program:

class HelloWorldProgram
{
    public static void Main()
    {
        System.Console.WriteLine("Hello, world!"); // prints some text on to the screen
        System.Console.ReadKey(); /* waits for the user
        to press a key
        */
    }
}

Let's go through each line and see what they do:

• class HelloWorldProgram defines a class named "HelloWorldProgram". At this point, you can think of a class as a group of methods.
• public static void Main() defines a method named "Main". A method is simply a code block (a container) containing some statements. The Main() method is special because it is the first thing that is run when your program is started.
• System.Console.WriteLine("Hello, world!"); is a statement. A statement performs an action, which in this case is printing (outputting) "Hello, world!" to the screen.
• System.Console.ReadKey(); is another statement. This time, it waits for the user to press a key.
• After the last statement is executed, the program terminates.

Here's what should have happened:

• You start the program.
• The program outputs "Hello, world!" and waits.
• You press a key.
• The program closes.

Comments

Comments are pieces of text which are ignored by the compiler. There are three types of comments, two of which were used in the hello world program above.

1. A single line comment is produced by using a double slash (//) and tells the compiler to ignore the rest of the line.
2. A multiline comment is started by using a slash and an asterisk (/*) and ended using an asterisk and a slash (*/). The compiler ignores everything in between, even if the comment stretches over multiple lines (hence the name).
3. A documentation comment is used to document classes, properties, and methods. They start with three slashes (///) and use various XML tags.

Although comments are useful for describing code, they should not be used to simply restate what the code does, i.e.:

int number = 12; // declares a variable and assigns 12 to it

Console.WriteLine(number); // prints 12 to the console

Instead, they should be used to explain why a code does something that way.

int number = 12; // 12 is the number of months in a year.

Console.WriteLine(number);

There are other solutions to this, as you will see soon.