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XamlReader.LoadAsync Method (XmlReader)

Reads the XAML markup in the specified XmlReader and returns the root of the corresponding object tree.

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

public Object LoadAsync(
	XmlReader reader
You cannot use methods in XAML.


Type: System.Xml.XmlReader

An XmlReader that has loaded the markup to load.

Return Value

Type: System.Object
The root of the deserialized tree.


reader is null.


Multiple load operations are performed concurrently with the same XamlReader.

An asynchronous XAML load operation will initially return an object that is purely the root object. Asynchronously, XAML parsing then continues, and any child objects are filled in under the root. This is in contrast to the typical XAML processing behavior of making sure that all properties of an object including all child collections are filled before returning an element and reporting it as loaded. That behavior equates to a bottom-up methodology for creating the tree where the root object is the last object to become available.

You typically would assign the returned object to some location in your application's object tree, with the knowledge that content might still be filling in and might cause incremental layout updates if the entire content is exposed as part of the UI. For this reason it is typical to isolate or virtualize any asynchronously loaded objects from XAML, and to perhaps change application state when LoadCompleted is handled.

In order for LoadAsync to load markup asynchronously, the root element in the XAML markup must contain the attribute and value x:SynchronousMode="Async". The value is treated as case sensitive. If the markup does not contain x:SynchronousMode="Async", no exception is thrown, and the call is processed as a synchronous load.

Only one asynchronous load operation per instance of the XamlReader class can be performed at a time. If more than one asynchronous operation is attempted on the same instance of the XamlReader class an InvalidOperationException is thrown.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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

.NET Framework

Supported in: 3.5, 3.0