XNamespace Class
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Represents an XML namespace. This class cannot be inherited.
Assembly: System.Xml.Linq (in System.Xml.Linq.dll)
The XNamespace type exposes the following members.
| 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/). |
| 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().) |
| 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. |
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 nullptr.
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:
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:
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 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")
);
Dim e As XElement = New XElement("{http://www.adventure-works.com}Root", _ New XAttribute("{http://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.