Using WebClient and AssemblyPart we can dynamically load any assemblies. This is greate techniques to use for designing plug and play type of Silverlight application. Also this is greate optimazation technique to make the xap file smaller and lazy load assemblies that might contain business logic.

Imagine that you have silverlight that does not require redeployment and only thing you have to redeploy is your reflectively loaded assemblies during runtime!