When you apply an animation to a property using the Compose HandoffBehavior, any clocks objects previously associated with that property continue to consume system resources; the timing system will not remove these clocks automatically.

To avoid performance issues when you apply a large number of clocks using HandofffBehavior.Compose, you should remove composing clocks from the animated property after they complete. There are several ways to remove a clock.

1. To remove all clocks from a property, use the ApplyAnimationClock or BeginAnimation method of the animation object. Specify the property being animated as the first parameter, and a null reference (Nothing in Visual Basic) as the second. This will remove all animation clocks from the property.
2. To remove a specific AnimationClock from a list of clocks, use the Controller property of the AnimationClock to retrieve a ClockController, then call the ClockController.Remove() method of the ClockController. This is typically done in the Completed event handler for a clock. Note that only root clocks can be controlled by a ClockController; the Controller property of a child Clock will return a null reference (Nothing in Visual Basic). Note also that the Completed event will not be called if the effective duration of the clock is forever. In that case, the user will need to determine when to call ClockController.Remove().

This is primarily an issue for animations on objects that have a long lifetime. When an object is garbage collected, its clocks will also be disconnected and garbage collected.