Custom Controls for Silverlight 2
Silverlight 2 features a rich and robust control model that is the basis for the controls included in the platform and for third-party control packages. You can also use this control model to build controls of your own.
In the August 2008 issue of MSDN Magazine, Jeff Prosise describes how to build a SimpleButton control that duplicates important aspects of the built-in Button control's look and behavior and provides a helpful first look at control development, Silverlight style.
Don’t forget to browse the example code online.