Silverlight 3 has nice feature to reduce the XAP package size of application by providing external assembly parts. To enable this feature use Silverlight project properties: When this enabled, most of Microsoft assemblies will not reside inside XAP package, but as ZIP files alongside the XAP itself. The application manifest will point to those ZIP files. This will enable browser caching mechanism. Actually, compiler “decides” which assembly will could be used as external ZIP assembly by presence...