UIElement.RemoveHandler(RoutedEvent, Delegate) Method

Definition

Namespace:: System.Windows

Assembly:: PresentationCore.dll

Removes the specified routed event handler from this element.

public:
 virtual void RemoveHandler(System::Windows::RoutedEvent ^ routedEvent, Delegate ^ handler);

public void RemoveHandler (System.Windows.RoutedEvent routedEvent, Delegate handler);

abstract member RemoveHandler : System.Windows.RoutedEvent * Delegate -> unit
override this.RemoveHandler : System.Windows.RoutedEvent * Delegate -> unit

Public Sub RemoveHandler (routedEvent As RoutedEvent, handler As Delegate)

Parameters

routedEvent: RoutedEvent

The identifier of the routed event for which the handler is attached.

handler: Delegate

The specific handler implementation to remove from the event handler collection on this element.

Implements

RemoveHandler(RoutedEvent, Delegate)

Examples

The following example uses RemoveHandler as part of an event wrapper definition.

public static readonly RoutedEvent TapEvent = EventManager.RegisterRoutedEvent(
    "Tap", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(MyButtonSimple));

// Provide CLR accessors for the event
public event RoutedEventHandler Tap
{
        add { AddHandler(TapEvent, value); } 
        remove { RemoveHandler(TapEvent, value); }
}

Public Shared ReadOnly TapEvent As RoutedEvent = EventManager.RegisterRoutedEvent("Tap", RoutingStrategy.Bubble, GetType(RoutedEventHandler), GetType(MyButtonSimple))

' Provide CLR accessors for the event
Public Custom Event Tap As RoutedEventHandler
    AddHandler(ByVal value As RoutedEventHandler)
        Me.AddHandler(TapEvent, value)
    End AddHandler

    RemoveHandler(ByVal value As RoutedEventHandler)
        Me.RemoveHandler(TapEvent, value)
    End RemoveHandler

    RaiseEvent(ByVal sender As Object, ByVal e As RoutedEventArgs)
        Me.RaiseEvent(e)
    End RaiseEvent
End Event

Remarks

The most common scenario for using this API is when you implement the common language runtime (CLR) "wrapper" event that is associated with a custom routed event, specifically when you implement the "remove" logic for handlers at the CLR level. The example that follows this remarks section illustrates this scenario.

Calling this method has no effect if there were no handlers registered with criteria that matches the input parameters for the method call.

If more than one handler is attached that matched the criteria, only the first handler in the event handler store is removed. This behavior is consistent with CLR behavior of the -= operator.

Neither routedEvent nor handler may be null. Attempting to provide either value as null will raise an exception.

This method ignores the handledEventsToo parameter information, which is provided if the handler was first added with the AddHandler(RoutedEvent, Delegate, Boolean) signature that enables handling of already-handled events. Either type of handler is removed.