Binding.IsAsync Property

Gets or sets a value that indicates whether the Binding should get and set values asynchronously.

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

member IsAsync : bool with get, set
<object IsAsync="bool" .../>

Property Value

Type: System.Boolean
The default is a null reference (Nothing in Visual Basic).

Use the IsAsync property when the get accessor of your binding source property might take a long time. One example is an image property with a get accessor that downloads from the Web. Setting IsAsync to true avoids blocking the UI while the download occurs.

While waiting for the value to arrive, the binding reports the FallbackValue, if one is available, or the default value of the binding target property.

However, there should not be many scenarios where you need to use the IsAsync property. The .NET guidelines recommend against defining properties that are orders of magnitude slower than a field set would be. When you are creating your class, consider handling extremely slow operations outside of the get accessor and caching the result. For more information, see Choosing Between Properties and Methods.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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