XmlnsDefinitionAttribute Class

XmlnsDefinitionAttribute Class

This API supports the .NET Framework infrastructure and is not intended to be used directly from your code.

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Specifies a mapping in an assembly between an XML namespace identifier and a CLR namespace within that assembly.


Namespace:  System.Windows.Markup
Assembly:  System.Windows (in System.Windows.dll)

[AttributeUsageAttribute(AttributeTargets.Assembly, AllowMultiple = true)]
public sealed class XmlnsDefinitionAttribute : Attribute

The XmlnsDefinitionAttribute type exposes the following members.

Public methodXmlnsDefinitionAttributeInitializes a new instance of the XmlnsDefinitionAttribute class.

Public propertyAssemblyNameGets or sets the name of the assembly that contains the ClrNamespace.
Public propertyClrNamespaceGets the CLR namespace that is mapped to XmlNamespace by the attribute.
Public propertyXmlNamespaceGets the XML namespace (xmlns) that is mapped to ClrNamespace by the attribute.

Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)


App assemblies are delay-loaded to improve start time. Consequently, this class is not supported in Windows Phone OS 7.1 or in Windows Phone 8.

In a XAML file, if the xmlns attribute for an element tag or attribute matches the XmlNamespace in the XmlnsDefinitionAttribute, a XAML processor can use the ClrNamespace and AssemblyName stored in the XmlnsDefinitionAttribute to check whether the element or attribute matches any type inside the namespace in the assembly. This is how a XAML processor can discover the assemblies that define the types that are created when it processes XAML into an object tree. In particular, a XAML processor uses XmlnsDefinitionAttribute from known and loaded reference assemblies when the namespace identifier is a URI, and the namespace is not defined by an explicit CLR-namespace/assembly combination.

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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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