name space in c#

A namespace is a logical container of all the user defined type.
* A namespace may contain one or more of following type.
*With a namespace ,you can declare one or more of following types.

• another namespace
  
• class
  
• interface
  
• struct
  
• enum
  
• delegate
  

 Note:Default namespace in c# is "unnamed" or "global namespace"

Program that demonstrates namespace use: C#

using System;
using A.B.C;

namespace E
{
    using D;

    class Program
    {
 static void Main()
 {
     // Can access CClass type directly from A.B.C.
     CClass var1 = new CClass();

     // Can access DClass type from D.
     DClass var2 = new DClass();

     // Must explicitely specify F namespace.
     F.FClass var3 = new F.FClass();

     // Display types.
     Console.WriteLine(var1);
     Console.WriteLine(var2);
     Console.WriteLine(var3);
 }
    }
}

namespace A
{
    namespace B
    {
 namespace C
 {
     public class CClass
     {
     }
 }
    }
}

namespace D
{
    public class DClass
    {
    }
}

namespace F
{
    public class FClass
    {
    }
}