This documentation is archived and is not being maintained.

XamlReader.LoadAsync Method (Stream)

Reads the XAML input in the specified Stream and returns the root of the corresponding object tree.

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

public Object LoadAsync(
	Stream stream


Type: System.IO.Stream
The stream containing the XAML input to load.

Return Value

Type: System.Object
The object that is the root of the created object tree.


stream is null.


Multiple load operations are pending 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 WPF XAML processing behavior and its interaction with WPF concepts of object lifetime. In the typical (non-async) interaction, 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 WPF 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 use application-specific logic or application state to notify when LoadCompleted is handled.

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

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.

.NET Framework

Supported in: 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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