The OnMouseEnter method is called before any event handler for the MouseEnter event is called. This method allows derived classes to handle the MouseEnter event without attaching a delegate. This is the preferred technique for handling the event in a derived class.
This implementation marks the MouseEnter event as handled by setting the Handled property of the event data to true.
Notes to Inheritors
When overriding OnMouseEnter method in a derived class, be sure to call the base class’s OnMouseEnter method so that registered delegates receive the event.