What can I do inside CompositionTarget.Rendering?
问题 The CompositionTarget.Rendering event is the perfect thing to build a game's main loop upon. It basically fires at the rate of vsync (usually 60 Hz). Occurs just before the objects in the composition tree are rendered. The Rendering event is routed to the specified event handler after animation and layout have been applied to the composition tree. The per-frame animation how-to article explains a little bit more. Note that your event handler method is called after layout has been computed.