In this blog post, Tapas describes the various key points that need to be addressed while implementing a new control support in a Coded UI Test Plugin (a  WPF plugin in this case). A sample WPF Calendar control example gives an in-depth on the various implementation details.

 

For more details - http://blogs.msdn.com/b/tapas_sahoos_blog/archive/2010/12/10/adding-new-control-support-in-a-coded-ui-test-plugin.aspx