The first thing to understand is how to tap into the touch events from the hardware to Silverlight. Understanding this at the beginning of your application development can be a critical step. The key reason for this is unlike other input events (i.e., MouseLeftButtonDown, etc.) which can be added to individual UIElements in an application, the touch event is an application-wide event.
There is one primary event: FrameReported. This event is what gets fired when the hardware sends the touch events to the runtime. The Touch class is a static class for the sole reason of this FrameReported API. To wire it up in your application you can use code like this:1: Touch.FrameReported += new TouchFrameEventHandler(Touch_FrameReported);
And now you have to write your event handler.