July 28, 2014
Occurs when a touch event occurs outside the bounding area of a UIElement.
Assembly: System.Windows (in System.Windows.dll)
XMLNS for XAML: Not mapped to an xmlns.
The event is raised in response to a touch event occurring outside the object's bounding area.
You can define multiple events for objects in XAML content. However, if a child object and its parent object both define a event, the parent object's event occurs before the child object's event. This is not a case of a bubbling event; it indicates only that entered touch event has occurred for both objects, potentially at different times depending on the object layout and composition of the visual tree.
Unlike the MouseEnter event, the event does not provide the touch position in event data, because the position of the touch event relative to the object is unknown when it is out of bounds. Because it is always null, you generally should not use the event data from your event handler, although you may still be interested in the sender parameter.
events do not route, they can only be handled on the element that raises them.
MouseLeave and OnMouseLeave
Controls that inherit can provide handling for the event that acts as handler for all instances, by overriding the OnMouseLeave method. OnMouseLeave can be useful either for setting visual state, or for public or internal state properties. For instance, Slider implements OnMouseLeave in order to check the Thumb element's value for IsDragging (which cancels a particular behavior mode), and also to set visual state. For more information, see OnMouseLeave.