Namespaces

Namespaces?

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
}

Example - Without the "using" keyword

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();
   }
}

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");

Example - With the "using" keyword

using System;
using first_space; // Importing here
using second_space; // Importing here

namespace first_space {
   class abc {
      public void func() {
         Console.WriteLine("Inside first_space");
      }
   }
}
namespace second_space {
   class efg {
      public void func() {
         Console.WriteLine("Inside second_space");
      }
   }
}   
class TestClass {
   static void Main(string[] args) {
      abc fc = new abc(); // Notice we are not using the fully qualified syntax
      efg sc = new efg(); // Notice we are not using the fully qualified syntax
      fc.func();
      sc.func();
      Console.ReadKey();
   }
}