What and how to use namespaces in C#

Namespaces are an organizational tool in the .NET framework that allows us to group related classes and other code elements under the same name.

Namespaces help prevent naming conflicts between different elements. For example, imagine two libraries that use the same name Client. With namespaces, we avoid conflict and ambiguity.

Creating a Namespace in .NET

Creating a Namespace in .NET is done by declaring the keyword namespace followed by the name we want to give it.

Then, inside the braces, we place the classes and other related programming elements.

namespace MyNamespace
{
    public class MyClass
    {
        // Class code
    }
}

Using Namespaces

To use a Namespace in a C# program, we can do it in two ways:

MyProgram.MyClass myObject = new MyProgram.MyClass();

using MyProgram;

// ...

MyClass myObject = new MyClass();

Nested Namespaces

Namespaces can be nested. That is, a Namespace can contain other Namespaces. This allows for a hierarchical organization of code (although it is not particularly common).

namespace Company
{
    namespace Project
    {
        public class MainClass
        {
            // Class code
        }
    }
}

To access MainClass, you can use Company.Project.MainClass or import the nested namespace:

using Company.Project;

public class SecondaryClass
{
    public void Method()
    {
        MainClass instance = new MainClass();
    }
}

Namespace Aliases

In some cases, it may be useful to define an alias for a Namespace. This is useful

• If the Namespace name is long
• If there are naming conflicts

To do this, we use the using keyword followed by an alias and the Namespace. Like this:

using Alias = Long.Namespace.Name;

public class ClassWithAlias
{
    public void Method()
    {
        Alias.Class instance = new Alias.Class();
    }
}

Static Namespaces

C# also allows importing static members of a class, known as using static. This is useful for accessing static methods and constants without having to specify the full class name.

using static System.Math;

public class Calculator
{
    public double CalculateHypotenuse(double a, double b)
    {
        return Sqrt(a * a + b * b);
    }
}