namespace (C# Reference)

The namespace keyword is used to declare a scope that contains a set of related objects. You can use a namespace to organize code elements and to create globally unique types.

namespace SampleNamespace
{
    class SampleClass { }

    interface SampleInterface { }

    struct SampleStruct { }

    enum SampleEnum { a, b }

    delegate void SampleDelegate(int i);

    namespace SampleNamespace.Nested
    {
        class SampleClass2 { }
    }
}

Remarks

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 referred to as 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 in 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:

namespace MyCompany.Proj1
{
    class MyClass
    {
    }
}

namespace MyCompany.Proj1
{
    class MyClass1
    {
    }
}

Example

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

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

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

• Namespaces (C# Programming Guide)

• Using Namespaces (C# Programming Guide)

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

C# Language Specification

For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.

See Also

Reference

C# Keywords

Namespace Keywords (C# Reference)

using (C# Reference)

Concepts

C# Programming Guide

Other Resources

C# Reference