Few days ago, I published one article on "Application Library Caching in Silverlight 4". In that article, we discussed about Library Caching concept in detail with a small demo. We discussed various parts of the AppManifest to support this feature for 3rd party libraries. But sometime you may need this feature for your own custom libraries too to reduce the XAP file size by separating the external assemblies in their own ZIP file, which will download by the app when it is require. Let us discuss on this topic today by a small example which will help you to understand how to prepare your dll library to support Library Caching by your application. Read more to learn about it.