RoutedEventArgs.Handled Property

Definition

Namespace:

System.Windows

Assembly:

PresentationCore.dll

Gets or sets a value that indicates the present state of the event handling for a routed event as it travels the route.

public:
 property bool Handled { bool get(); void set(bool value); };

public bool Handled { get; set; }

member this.Handled : bool with get, set

Public Property Handled As Boolean

Property Value

Boolean

If setting, set to true if the event is to be marked handled; otherwise false. If reading this value, true indicates that either a class handler, or some instance handler along the route, has already marked this event handled. false.indicates that no such handler has marked the event handled.

The default value is false.

Examples

The following example implements an event handler that marks the event handled.

protected override void OnPreviewMouseRightButtonDown(System.Windows.Input.MouseButtonEventArgs e)
{
    e.Handled = true; //suppress the click event and other leftmousebuttondown responders
    MyEditContainer ec = (MyEditContainer)e.Source;
    if (ec.EditState)
    { ec.EditState = false; }
    else
    { ec.EditState = true; }
    base.OnPreviewMouseRightButtonDown(e);
}

Protected Overrides Sub OnPreviewMouseRightButtonDown(ByVal e As System.Windows.Input.MouseButtonEventArgs)
    e.Handled = True 'suppress the click event and other leftmousebuttondown responders
    Dim ec As MyEditContainer = CType(e.Source, MyEditContainer)
    If ec.EditState Then
        ec.EditState = False
    Else
        ec.EditState = True
    End If
    MyBase.OnPreviewMouseRightButtonDown(e)
End Sub

Remarks

Marking the event handled will limit the visibility of the routed event to listeners along the event route. The event does still travel the remainder of the route, but only handlers specifically added with HandledEventsToo true in the AddHandler(RoutedEvent, Delegate, Boolean) method call will be invoked in response. Default handlers on instance listeners (such as those expressed in Extensible Application Markup Language (XAML)) will not be invoked. Handling events that are marked handled is not a common scenario.

If you are a control author defining your own events, the decisions you make regarding event handling at the class level will impact users of your control as well as any users of derived controls, and potentially other elements that are either contained by your control or that contain your control. For more information, see Marking Routed Events as Handled, and Class Handling.

In very rare circumstances it is appropriate to handle events where Handled is marked true, and modify the event arguments by changing Handled to false. This can be necessary in certain areas of input events of controls, such as key handling of KeyDown versus TextInput where low level and high level input events compete for the handling, and each is attempting to work with a different routing strategy.