C# namespaces provide a way to organize related classes and other types.

A namespace is a logical grouping which means the class with the same namespace can be in different assemblies or components.

using System;
using MyProject.MyGroup.MyNamespaceOne; // using directive
using MNTwo = MyProject.MyGroup.MyNamespaceTwo;  // namespace Alias


TestClass testOne = new TestClass();
testOne.TestMethodOne();

MNTwo.TestClass testTwo = new MNTwo.TestClass();
testTwo.TestMethodTwo();


namespace MyProject.MyGroup.MyNamespaceOne
{
    public class TestClass
    {
        public void TestMethodOne()
        {
            Console.WriteLine("this is from namespace: MyProject.MyGroup.MyNamespaceOne.");
        }
    }
}

namespace MyProject.MyGroup.MyNamespaceTwo
{
    public class TestClass
    {
        public void TestMethodTwo()
        {
            Console.WriteLine("this is from namespace: MyProject.MyGroup.MyNamespaceTwo");
        }
    }
}

Output:

this is from namespace: MyProject.MyGroup.MyNamespaceOne.
this is from namespace: MyProject.MyGroup.MyNamespaceTwo.