LookupPrefix Method
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IXmlNamespaceResolver.LookupPrefix Method (String)


Gets the prefix that is mapped to the specified namespace URI.

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

string LookupPrefix(
	string namespaceName


Type: System.String

The namespace URI whose prefix you wish to find.

Return Value

Type: System.String

The prefix that is mapped to the namespace URI; null if the namespace URI is not mapped to a prefix.

It is possible for a namespace URI to be mapped to multiple prefixes. Because the prefixes are not mapped in a predictable manner, you should not depend on getting back a particular prefix when a namespace URI is mapped to more than one prefix.


Namespace URI to prefix mappings can change from node to node in an XML document. You cannot depend on the result of a lookup being consistent from one node to the next.

The following table describes how the default and built-in namespaces are handled by the LookupPrefix method.


Return value





An empty namespace.

A default namespace that has not been defined.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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