ExtensionMethod.Net has over 300 C#  extension methods (over 100 are on the string class).  For an overview on extension methods visit this MSDN page or see my old post.

How to prevent a Silverlight .XAP from being cached…

To be safe one should add (and change) a query parameter after their Silverlight application to prevent the file from being cached. The HTML would look something like: <param name="source" value="ClientBin/MySilverlightApplication.xap?revision=2012011801"/> And the revision needs to be changed after every new build that is published.