David Anson demonstrates a different approach of implementing a Popup that overlays the entire Silverlight plug-in.
When it comes time to display a Popup
that overlays the entire Silverlight plug-in, most people do it the
same way. Unfortunately, although the typical approach appears correct
at first glance (and may even survive a test pass!), there are some
problems that are just about guaranteed to surface once the application
is released. The purpose of this post is to educate people about those
issues - and suggest an alternative approach that is easier to get
right.