Namespaces (C# Programming Guide)

Namespaces are heavily used in C# programming in two ways. First, .NET uses namespaces to organize its many classes, as follows:

System.Console.WriteLine("Hello World!");

System is a namespace and Console is a class in that namespace. The using keyword can be used so that the complete name is not required, as in the following example:

using System;

For more information, see the using Directive.

Second, declaring your own namespaces can help you control the scope of class and method names in larger programming projects. Use the namespace keyword to declare a namespace, as in the following example:

namespace SampleNamespace
    class SampleClass
        public void SampleMethod()
              "SampleMethod inside SampleNamespace");

The name of the namespace must be a valid C# identifier name.

Namespaces overview

Namespaces have the following properties:

  • They organize large code projects.
  • They are delimited by using the . operator.
  • The using directive obviates the requirement to specify the name of the namespace for every class.
  • The global namespace is the "root" namespace: global::System will always refer to the .NET System namespace.

C# language specification

For more information, see the Namespaces section of the C# language specification.

See also