Called before KeyUp event occurs.
Assembly: System.Windows (in System.Windows.dll)
The method is called before any event handler for the KeyUp event is called. This method allows derived classes to handle the KeyUp event without attaching a delegate. This is the preferred technique for handling the event in a derived class.Notes to Inheritors
If you override the method, you can prevent registered delegates from receiving events by setting Handled to true. For more information about routed events and the Handled property, see Events for Windows Phone 8.