Namespaces are heavily used in C# programming in two ways. First, the .NET Framework uses namespaces to organize its many classes, as follows:

System.Console.WriteLine("Hello World!");

System is a namespace and Console is a class contained within that namespace. The using keyword can be used so that the entire name is not required, like this:

using System;

Console.WriteLine("Hello");
Console.WriteLine("World!");

For more information, see the topic using Directive (C# Reference).

Second, declaring your own namespaces can help you control the scope of class and method names in larger programming projects. Use the namespace keyword to declare a namespace, as in the following example:

namespace SampleNamespace
{
   class SampleClass
   {
       public void SampleMethod()
       {
           System.Console.WriteLine(
             "SampleMethod inside SampleNamespace");
       }
   }
}

Namespaces Overview