C# Namespaces

Namespaces in C# are used to organize too many classes so that it can be easy to handle the application.

In a simple C# program, we use System.Console where System is the namespace and Console is the class. To access the class of a namespace, we need to use namespacename.classname. We can use using keyword so that we don't have to use complete name all the time.

In C#, global namespace is the root namespace. The global::System will always refer to the namespace "System" of .Net Framework.

C# namespace example

Let's see a simple example of namespace which contains one class "Program".

using System;
namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello Namespace!");
        }
    }
}

Output:

Hello Namespace!

C# namespace example: by fully qualified name

Let's see another example of namespace in C# where one namespace program accesses another namespace program.

using System;
namespace First {
public class Hello
{
    public void sayHello() { Console.WriteLine("Hello First Namespace"); }
}
}
namespace Second
{
    public class Hello
    {
        public void sayHello() { Console.WriteLine("Hello Second Namespace"); }
    }
}
public class TestNamespace
{
    public static void Main()
    {
        First.Hello h1 = new First.Hello();
        Second.Hello h2 = new Second.Hello();
        h1.sayHello();
        h2.sayHello();

    }
}

Output:

Hello First Namespace
Hello Second Namespace

C# namespace example: by using keyword

Let's see another example of namespace where we are using "using" keyword so that we don't have to use complete name for accessing a namespace program.

using System;
using First;
using Second;
namespace First {
public class Hello
{
    public void sayHello() { Console.WriteLine("Hello Namespace"); }
}
}
namespace Second
{
    public class Welcome
    {
        public void sayWelcome() { Console.WriteLine("Welcome Namespace"); }
    }
}
public class TestNamespace
{
    public static void Main()
    {
        Hello h1 = new Hello();
        Welcome w1 = new Welcome();
        h1.sayHello();
        w1.sayWelcome();
    }
}

Output: