namespace (C# Reference)

Within a namespace, you can declare one or more of the following types:

• another namespace

• class

• interface

• struct

• enum

• delegate

Whether or not you explicitly declare a namespace in a C# source file, the compiler adds a default namespace. This unnamed namespace, sometimes called the global namespace, is present in every file. Any identifier in the global namespace is available for use in a named namespace.

Namespaces implicitly have public access and this is not modifiable. For a discussion of the access modifiers you can assign to elements within a namespace, see Access Modifiers (C# Reference).

It is possible to define a namespace in two or more declarations. For example, the following example defines two classes as part of the MyCompany namespace:

// cs_namespace_keyword.cs
// compile with: /target:library
namespace MyCompany.Proj1 
{
    class MyClass 
    {
    }
}

namespace MyCompany.Proj1 
{
    class MyClass1 
    {
    }
}

The following example shows how to call a static method in a nested namespace.

// cs_namespace_keyword_2.cs
using System;
namespace SomeNameSpace
{
    public class MyClass 
    {
        static void Main() 
        {
            Nested.NestedNameSpaceClass.SayHello();
        }
    }

    // a nested namespace
    namespace Nested   
    {
        public class NestedNameSpaceClass 
        {
            public static void SayHello() 
            {
                Console.WriteLine("Hello");
            }
        }
    }
}

Output

Hello

For more information on using namespaces, see the following topics:

• Namespaces (C# Programming Guide)

• Using Namespaces (C# Programming Guide)

• How to: Use the Namespace Alias Qualifier (C# Programming Guide)

For more information, see the following sections in the C# Language Specification:

• 3.4.1 Namespace members

• 3.8 Namespace and type names

• 9 Namespaces

Reference

Concepts

Other Resources