A namespace is designed for providing a way to keep one set of names separate from another. The class names declared in one namespace does not conflict with the same class names declared in another.

 

Defining a Namespace

A namespace definition begins with the keyword namespace followed by the namespace name as follows −

namespace namespace_name {

   // code declarations

}

To call the namespace-enabled version of either function or variable, prepend the namespace name as follows −

namespace_name.item_name;

The following program demonstrates use of namespaces −

using System;

namespace first_space {

   class namespace_cl {

      public void func() {

         Console.WriteLine("Inside first_space");

      }

   }

}

namespace second_space {

   class namespace_cl {

      public void func() {

         Console.WriteLine("Inside second_space");

      }

   }

}

class TestClass {

   static void Main(string[] args) {

      first_space.namespace_cl fc = new first_space.namespace_cl();

      second_space.namespace_cl sc = new second_space.namespace_cl();

      fc.func();

      sc.func();

      Console.ReadKey();

   }

}

When the above code is compiled and executed, it produces the following result −

Inside first_space

Inside second_space

The using Keyword

The using keyword states that the program is using the names in the given namespace. For example, we are using the System namespace in our programs. The class Console is defined there. We just write −

Console.WriteLine ("Hello there");

We could have written the fully qualified name as −

System.Console.WriteLine("Hello there");

You can also avoid prepending of namespaces with the using namespace directive. This directive tells the compiler that the subsequent code is making use of names in the specified namespace. The namespace is thus implied for the following code −

Let us rewrite our preceding example, with using directive −

using System;

using first_space;

using second_space;

namespace first_space {

   class test1 {

      public void func() {

         Console.WriteLine("Inside first_space");

      }

   }

}

namespace second_space {

   class test2 {

      public void func() {

         Console.WriteLine("Inside second_space");

      }

   }

}   

class TestClass {

   static void Main(string[] args) {

      test1 fc = new test1();

      test2 sc