2.1 A First C Program

2.1 A First C# Program

Here is a simple C# program:

 namespace FirstProgram {   using System;   class Example {     static void Main ( ) {       Console.WriteLine ("Hello world!");     }   } } 

A C# program is composed of types (typically classes) that we organize into namespaces. Each type contains function members (typically methods and properties), as well as data members (typically fields). Methods contain a series of statements that are executed sequentially. In our program, we define a class named Example that contains a method named Main , which has a single statement that writes Hello world! to the console window. C# recognizes this method as the default entry point of execution, so that's where the program begins.

The Console class encapsulates standard input/output functionality, providing methods such as WriteLine . To use types from another namespace, use the using directive. Since the Console class resides in the System namespace, we write using System ; similarly, types from other namespaces could use our Example class by using FirstProgram .

In C#, there are no standalone functions; they are always associated with a type, or, as we will see, instances of that type. Our program is simple, and makes use of only static members, which means the member is associated with its type, rather than instances of its type. In addition, we make use of only void methods, which means these methods do not return a value.

Throughout this book, most of the examples contain this stub code:

 using System; class Test {   static void Main ( ) {     ...   } }