C# Hello World!
// A "Hello World!" program in C#
class Hello
{
static void Main()
{
System.Console.WriteLine("Hello
World!");
}
}
Comments
The first line contains a comment:
// A "Hello World!" program in C#
The characters // convert the rest of the line to a comment.
You can also comment a block of text by placing it between the characters /* and */, for example:
/* A "Hello World!" program in C#.
This program displays the string "Hello World!" on the screen. */
The
Main Method
The C# program must contain a Main method,
in which control starts and ends. The Main method is where you create objects and
execute other methods.
The Main method is a static method that resides
inside a class or a struct. In the "Hello World!" example, it resides
inside the Hello class. Declare the Main method
in one of the following ways:
· static void Main()
· {
· ...
· }
- It can also
return an int:
· static int Main()
· {
· ...
· return 0;
· }
- With both of
the return types, it can take arguments:
· static int Main(string[] args)
· {
· ...
· return 0;
· }
-or-
static void Main(string[] args)
{
...
}
The parameter of the Main method is a string array
that represents the command-line arguments used to invoke the program. Notice
that, unlike C++, this array does not include the name of the executable (exe)
file.
Input
and Output
C# programs generally use the input/output services provided by
run-time library of the .NET Framework. The statement: System.Console.WriteLine("Hello World!"); uses the WriteLine method, one of the output methods of the Console class in the run-time library. It displays
its string parameter on the standard output stream followed by a new line.
Other Console methods are used for different input and
output operations. If you include the using System; statement at the beginning of the program,
you can directly use the System classes and methods without fully
qualifying them. For example:
Console.WriteLine("Hello World!");