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