DataContextChangedEventArgs.Handled property

Applies to Windows and Windows Phone

Gets or sets a value that influences whether another DataContextChanged event should be fired from child elements that inherit the DataContext value and detect that the value has changed.

Syntax


public bool Handled { get; set; }

Property value

Type: System.Boolean [.NET] | Platform::Boolean [C++]

true to prevent further DataContextChanged events from being fired for each child FrameworkElement that inherits the DataContext value. You would do this to indicate to other handlers that the necessary logic for responding to the data context change has already been performed. false to permit the event to be fired by each immediate child FrameworkElement in the element tree that detects a change to the inherited DataContext value. The default is false.

Remarks

The FrameworkElement.DataContext property has a built-in behavior whereby its value inherits to all FrameworkElement child elements of a FrameworkElement where a DataContext value is set. This behavior enables a set of related elements to use the same context to bind to different source properties, which is particularly useful for item templates, data templates, and other data binding scenarios. Because DataContext inherits, there's potential for each FrameworkElement that uses the inherited value to fire another DataContextChanged event. That event is sourced from the inheriting element, not the parent element, once the element detects that its inherited DataContext value has changed. If you don't want this behavior, you should handle the DataContextChanged event on the parent source, where the event will occur first. As part of your handler logic, set the value of the Handled property in the DataContextChangedEventArgs event data to true. That action will prevent the event from routing to child elements.

Note  DataContextChanged has routing behavior but isn't a true routed event (it does not have a RoutedEvent identifier). Also, it routes from parent to child whereas the true routed events route from child to parent. If you're familiar with Windows Presentation Foundation (WPF), DataContextChanged might be considered a tunneling routing event by the WPF event routing definitions.

Requirements

Minimum supported client

Windows 8.1

Minimum supported server

Windows Server 2012 R2

Minimum supported phone

Windows Phone 8.1 [Windows Runtime apps only]

Namespace

Windows.UI.Xaml
Windows::UI::Xaml [C++]

Metadata

Windows.winmd

See also

DataContextChangedEventArgs
FrameworkElement.DataContext

 

 

Show:
© 2014 Microsoft