EventManager.RegisterClassHandler Method

Definition

Namespace:

System.Windows

Assembly:

PresentationCore.dll

Registers a class handler for a particular routed event.

Overloads

RegisterClassHandler(Type, RoutedEvent, Delegate)	Registers a class handler for a particular routed event.
RegisterClassHandler(Type, RoutedEvent, Delegate, Boolean)	Registers a class handler for a particular routed event, with the option to handle events where event data is already marked handled.

RegisterClassHandler(Type, RoutedEvent, Delegate)

Registers a class handler for a particular routed event.

public:
 static void RegisterClassHandler(Type ^ classType, System::Windows::RoutedEvent ^ routedEvent, Delegate ^ handler);

public static void RegisterClassHandler (Type classType, System.Windows.RoutedEvent routedEvent, Delegate handler);

static member RegisterClassHandler : Type * System.Windows.RoutedEvent * Delegate -> unit

Public Shared Sub RegisterClassHandler (classType As Type, routedEvent As RoutedEvent, handler As Delegate)

Parameters

classType

Type

The type of the class that is declaring class handling.

routedEvent

RoutedEvent

The routed event identifier of the event to handle.

handler

Delegate

A reference to the class handler implementation.

Examples

The following example adds a handler for PreviewMouseRightButtonDownEvent, calling RegisterClassHandler.

static MyEditContainer()
{
  EventManager.RegisterClassHandler(typeof(MyEditContainer), PreviewMouseRightButtonDownEvent, new RoutedEventHandler(LocalOnMouseRightButtonDown));
}
internal static void LocalOnMouseRightButtonDown(object sender, RoutedEventArgs e)
{
  MessageBox.Show("this is invoked before the On* class handler on UIElement");
  //e.Handled = true; //uncommenting this would cause ONLY the subclass' class handler to respond
}

Shared Sub New()
  EventManager.RegisterClassHandler(GetType(MyEditContainer), PreviewMouseRightButtonDownEvent, New RoutedEventHandler(AddressOf LocalOnMouseRightButtonDown))
End Sub
Friend Shared Sub LocalOnMouseRightButtonDown(ByVal sender As Object, ByVal e As RoutedEventArgs)
  MessageBox.Show("this is invoked before the On* class handler on UIElement")
  'e.Handled = True //uncommenting this would cause ONLY the subclass' class handler to respond
End Sub

Remarks

Class handling is a feature that is available for routed events, including attached events that are implemented with routed event backing. A class handler is like a static handler that exists for all instances of the class. Because the handler is static, you cannot change instance properties directly with a class handler, but you can access instances through the sender parameter and/or the event data.

Class handlers are invoked before instance handlers. You can implement a class handler that has the behavior of marking the event as handled. Therefore, instance handlers for a class-handled event are not invoked unless the instance handlers register specifically for handled events.

Many of the WPF base element events provide class handling virtual methods. By overriding these methods in classes that inherit the base classes, you can implement class handling without calling RegisterClassHandler in static constructors. These class handling methods typically exist for input events and have names that start with "On" and end with the name of the event being class handled.

For more information about class handling, see Marking Routed Events as Handled, and Class Handling.

Using this signature, class handlers will be registered to invoke only in response to unhandled events. You can also register class handlers to invoke even if the event arguments are marked handled, by using the RegisterClassHandler(Type, RoutedEvent, Delegate, Boolean) signature, with handledEventsToo set to true.

RegisterClassHandler(Type, RoutedEvent, Delegate, Boolean)

Registers a class handler for a particular routed event, with the option to handle events where event data is already marked handled.

public:
 static void RegisterClassHandler(Type ^ classType, System::Windows::RoutedEvent ^ routedEvent, Delegate ^ handler, bool handledEventsToo);

public static void RegisterClassHandler (Type classType, System.Windows.RoutedEvent routedEvent, Delegate handler, bool handledEventsToo);

static member RegisterClassHandler : Type * System.Windows.RoutedEvent * Delegate * bool -> unit

Public Shared Sub RegisterClassHandler (classType As Type, routedEvent As RoutedEvent, handler As Delegate, handledEventsToo As Boolean)

Parameters

classType

Type

The type of the class that is declaring class handling.

routedEvent

RoutedEvent

The routed event identifier of the event to handle.

handler

Delegate

A reference to the class handler implementation.

handledEventsToo

Boolean

true to invoke this class handler even if arguments of the routed event have been marked as handled; false to retain the default behavior of not invoking the handler on any marked-handled event.

Remarks

Class handling is a feature that is available for routed events, including attached events that are implemented with routed event backing. A class handler is like a static handler that exists for all instances of the class. Because the handler is static, you cannot change instance properties directly with a class handler, but you can access instances through the sender parameter and/or the event data.

Class handlers are invoked before instance handlers. You can implement a class handler that has the behavior of marking the event as handled. Therefore, instance handlers for a class-handled event are not invoked unless the instance handlers register specifically for handled events.

Many of the WPF base element events provide class handling virtual methods. By overriding these methods in classes that inherit the base classes, you can implement class handling without calling RegisterClassHandler in static constructors. These class handling methods typically exist for input events and have names that start with "On" and end with the name of the event being class handled.

For more information about class handling, see Marking Routed Events as Handled, and Class Handling.

Using this signature, class handlers can be registered to invoke upon handled events, by setting handledEventsToo set to true. Generally, you should do this only if there is a known handling issue you are trying to work around, such as input system handling from mouse or keyboard events.