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 in that namespace. The using keyword can be used so that the complete name is not required, as in the following example:

using System;

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

For more information, see 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");
        }
    }
}