Article
11/17/2011

XNamespace Class

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Represents an XML namespace. This class cannot be inherited.

Inheritance Hierarchy

System.Object
System.Xml.Linq.XNamespace

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

Syntax

'Declaration
Public NotInheritable Class XNamespace

public sealed class XNamespace

The XNamespace type exposes the following members.

Properties

	Name	Description
	NamespaceName	Gets the Uniform Resource Identifier (URI) of this namespace.
	None	Gets the XNamespace object that corresponds to no namespace.
	Xml	Gets the XNamespace object that corresponds to the XML URI (http://www.w3.org/XML/1998/namespace).
	Xmlns	Gets the XNamespace object that corresponds to the xmlns URI (http://www.w3.org/2000/xmlns/).

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Methods

	Name	Description
	Equals	Determines whether the specified XNamespace is equal to the current XNamespace. (Overrides Object.Equals(Object).)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
	Get	Gets an XNamespace for the specified Uniform Resource Identifier (URI).
	GetHashCode	Gets a hash code for this XNamespace. (Overrides Object.GetHashCode().)
	GetName	Returns an XName object created from this XNamespace and the specified local name.
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns the URI of this XNamespace. (Overrides Object.ToString().)

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Operators

	Name	Description
	Addition	Combines an XNamespace object with a local name to create an XName.
	Equality	Returns a value indicating whether two instances of XNamespace are equal.
	Implicit(String to XNamespace)	Converts a string containing a Uniform Resource Identifier (URI) to an XNamespace.
	Inequality	Returns a value indicating whether two instances of XNamespace are not equal.

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Remarks

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 nulla null reference (Nothing in Visual Basic).

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:

Dim output As New StringBuilder
Dim aw As XNamespace = "https://https://www.adventure-works.com"
Dim root As XElement = New XElement(aw + "Root", "Content")
output.Append(root)
output.Append(Environment.NewLine)

OutputTextBlock.Text = output.ToString()

StringBuilder output = new StringBuilder();
XNamespace aw = "https://https://www.adventure-works.com";
XElement root = new XElement(aw + "Root", "Content");
output.Append(root + Environment.NewLine);

OutputTextBlock.Text = output.ToString();

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:

Dim output As New StringBuilder
Dim aw As XNamespace = "https://www.adventure-works.com"
Dim root As XElement = New XElement(aw + "Root", _
    New XAttribute(XNamespace.Xmlns + "aw", "https://www.adventure-works.com"), _
    "Content")
output.Append(root)
output.Append(Environment.NewLine)

OutputTextBlock.Text = output.ToString()

StringBuilder output = new StringBuilder();
XNamespace aw = "https://www.adventure-works.com";
XElement root = new XElement(aw + "Root",
    new XAttribute(XNamespace.Xmlns + "aw", "https://www.adventure-works.com"),
    "Content");
output.Append(root + Environment.NewLine);

OutputTextBlock.Text = output.ToString();

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:

Dim output As New StringBuilder
Dim aw As XNamespace = "https://https://www.adventure-works.com"
Dim root As XElement = New XElement(aw + "Root", _
    New XAttribute("xmlns", "https://https://www.adventure-works.com"), _
    New XElement(aw + "Child", "content") _
)
output.Append(root)
output.Append(Environment.NewLine)

OutputTextBlock.Text = output.ToString()

StringBuilder output = new StringBuilder();
XNamespace aw = "https://https://www.adventure-works.com";
XElement root = new XElement(aw + "Root",
    new XAttribute("xmlns", "https://https://www.adventure-works.com"),
    new XElement(aw + "Child", "content")
);
output.Append(root + Environment.NewLine);

OutputTextBlock.Text = output.ToString();

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("{https://www.adventure-works.com}Root",
     new XAttribute("{https://www.adventure-works.com}Att", "content")
);

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

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.

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Thread Safety

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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