XNamespace Class

Represents an XML namespace. This class cannot be inherited.

System.Object
  System.Xml.Linq.XNamespace

Namespace:  System.Xml.Linq
Assembly:  System.Xml.Linq (in System.Xml.Linq.dll)

public sealed class XNamespace

The XNamespace type exposes the following members.

  NameDescription
Public propertySupported by the XNA FrameworkNamespaceNameGets the Uniform Resource Identifier (URI) of this namespace.
Public propertyStatic memberSupported by the XNA FrameworkNoneGets the XNamespace object that corresponds to no namespace.
Public propertyStatic memberSupported by the XNA FrameworkXmlGets the XNamespace object that corresponds to the XML URI (http://www.w3.org/XML/1998/namespace).
Public propertyStatic memberSupported by the XNA FrameworkXmlnsGets the XNamespace object that corresponds to the xmlns URI (http://www.w3.org/2000/xmlns/).
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  NameDescription
Public methodSupported by the XNA FrameworkEqualsDetermines whether the specified XNamespace is equal to the current XNamespace. (Overrides Object.Equals(Object).)
Protected methodSupported by the XNA FrameworkFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodStatic memberSupported by the XNA FrameworkGetGets an XNamespace for the specified Uniform Resource Identifier (URI).
Public methodSupported by the XNA FrameworkGetHashCodeGets a hash code for this XNamespace. (Overrides Object.GetHashCode().)
Public methodSupported by the XNA FrameworkGetNameReturns an XName object created from this XNamespace and the specified local name.
Public methodSupported by the XNA FrameworkGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by the XNA FrameworkMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by the XNA FrameworkToStringReturns the URI of this XNamespace. (Overrides Object.ToString().)
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  NameDescription
Public operatorStatic memberSupported by the XNA FrameworkAdditionCombines an XNamespace object with a local name to create an XName.
Public operatorStatic memberSupported by the XNA FrameworkEqualityReturns a value indicating whether two instances of XNamespace are equal.
Public operatorStatic memberSupported by the XNA FrameworkImplicit(String to XNamespace)Converts a string containing a Uniform Resource Identifier (URI) to an XNamespace.
Public operatorStatic memberSupported by the XNA FrameworkInequalityReturns a value indicating whether two instances of XNamespace are not equal.
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This class represents the XML construct of namespaces.

Every XName contains an XNamespace. Even if an element is not in a namespace, the element's XName still contains a namespace, XNamespace.None. The XName.Namespace property is guaranteed to not be null.

Creating an XNamespace Object

The most common way to create an XNamespace object is to simply assign a string to it. You can then combine the namespace with a local name by using the override of the addition operator. The following example shows this idiom:

XNamespace aw = "http://www.adventure-works.com";
XElement root = new XElement(aw + "Root", "Content");
Console.WriteLine(root);

However, in Visual Basic, you would typically declare a global default namespace, as follows:

Imports <xmlns='http://www.adventure-works.com'>

Module Module1
    Sub Main()
        Dim root As XElement = _
            <Root>Content</Root>
        Console.WriteLine(root)
    End Sub
End Module

This example produces the following output:

<Root xmlns="http://www.adventure-works.com">Content</Root>

Assigning a string to an XNamespace uses the implicit conversion from String.

See How to: Create a Document with Namespaces (C#) (LINQ to XML) for more information and examples.

See Namespaces in Visual Basic (LINQ to XML) for more information on using namespaces in Visual Basic.

Controlling Namespace Prefixes

If you create an attribute that declares a namespace, the prefix specified in the attribute will be persisted in the serialized XML. To create an attribute that declares a namespace with a prefix, you create an attribute where the namespace of the name of the attribute is Xmlns, and the name of the attribute is the namespace prefix. The value of the attribute is the URI of the namespace. The following example shows this idiom:

XNamespace aw = "http://www.adventure-works.com";
XElement root = new XElement(aw + "Root",
    new XAttribute(XNamespace.Xmlns + "aw", "http://www.adventure-works.com"),
    "Content");
Console.WriteLine(root);

In Visual Basic, instead of creating a namespace node to control namespace prefixes, you would typically use a global namespace declaration:

Imports <xmlns:aw='http://www.adventure-works.com'>

Module Module1
    Sub Main()
        Dim root As XElement = _
            <aw:Root>Content</aw:Root>
        Console.WriteLine(root)
    End Sub
End Module

This example produces the following output:

<aw:Root xmlns:aw="http://www.adventure-works.com">Content</aw:Root>

For more information, see How to: Control Namespace Prefixes (C#) (LINQ to XML).

Creating a Default Namespace

When constructing an attribute that will be a namespace, if the attribute name has the special value of "xmlns", then when the XML tree is serialized, the namespace will be declared as the default namespace. The special attribute with the name of "xmlns" itself is not in any namespace. The value of the attribute is the namespace URI.

The following example creates an XML tree that contains an attribute that is declared in such a way that the namespace will become the default namespace:

XNamespace aw = "http://www.adventure-works.com";
XElement root = new XElement(aw + "Root",
    new XAttribute("xmlns", "http://www.adventure-works.com"),
    new XElement(aw + "Child", "content")
);
Console.WriteLine(root);

In Visual Basic, instead of creating a namespace node to create a default namespace, you would typically use a global default namespace declaration:

Imports <xmlns='http://www.adventure-works.com'>

Module Module1
    Sub Main()
        Dim root As XElement = _
            <Root>
                <Child>content</Child>
            </Root>
        Console.WriteLine(root)
    End Sub
End Module

This example produces the following output:

<Root xmlns="http://www.adventure-works.com">
  <Child>content</Child>
</Root>

XNamespace Atomization

XNamespace objects are guaranteed to be atomized; that is, if two XNamespace objects have exactly the same URI, they will share the same instance. The equality and comparison operators are provided explicitly for this purpose.

Using Expanded Names

Another way to specify a namespace and a local name is to use an expanded name in the form {namespace}name:

[C#]

XElement e = new XElement("{http://www.adventure-works.com}Root",
     new XAttribute("{http://www.adventure-works.com}Att", "content")
);
Console.WriteLine(e);
Dim e As XElement = New XElement("{http://www.adventure-works.com}Root", _
     New XAttribute("{http://www.adventure-works.com}Att", "content") _
)
Console.WriteLine(e)

This example produces the following output:

<Root p1:Att="content" xmlns:p1="http://www.adventure-works.com" xmlns="http://www.adventure-works.com" />

This approach has performance implications. Each time that you pass a string that contains an expanded name to LINQ to XML, it must parse the name, find the atomized namespace, and find the atomized name. This process takes CPU time. If performance is important, you may want to use a different approach.

With Visual Basic, the recommended approach is to use XML literals, which does not involve the use of expanded names.

.NET Framework

Supported in: 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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