This implementation does not change the handled state (the Handled property) of the DragDelta event data.
Notes to Inheritors:
This method can be overridden to customize the way a Slider processes Thumb movements. If you override OnThumbDragDelta, always call the base implementation in your OnThumbDragDelta implementation. Failure to call the base implementation prevents base classes from handling the event with a class handler, which might change the run-time behavior of the final class. You can call the base implementation either before or after your special handling, depending on your requirements.