Jesse Bishop demonstrates how to dynamically set or change the visual theme for a Silverlight application at runtime.
The scenario is generally that an application has many possible themes, and needs to pick one depending on, for instance, a particular user or client who has logged in. What if these themes are huge, or there are hundreds of them? You probably wouldn’t want to bloat the downloaded .xap file by including every theme for every user. So, some approach is needed that lets us target a specific theme to download – at runtime – that isn’t in the application’s resources.