C# 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

The using Keyword

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

using System;
using System.ComponentModel;

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();
        //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:

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

using System;
using System.ComponentModel;
using first_space;
using second_space;

namespace first_space
{
    public static class abc
    {
        public static 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)
    {
        efg sc = new efg();
        abc.func();
        sc.func();
        Console.ReadKey();
        //Inside first_space
        //Inside second_space
    }
}

Nested Namespaces

You can define one namespace inside another namespace as follows:

using System;
using System.ComponentModel;
using first_space;
using first_space.second_space;
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();
        efg sc = new efg();
        fc.func();
        sc.func();
        Console.ReadKey();
        //Inside first_space
        //Inside second_space
    }
}