I'm trying to implement a plugable architecture in asp.net MVC. I have based my modules on the following article - http://www.wynia.org/wordpress/2008/12/aspnet-mvc-plugins. I have a DLL that contains a simple controller, and a view. The view is an embedded resource within the DLL. The problem I'm having is, if I drop the DLL in the bin directory of my MVC application manually, then everything works perfectly i.e. the assembly loads correctly. But when I copy the DLL from a file upload input box (via a web form) into the bin directoy, I get an error (The module was expected to contain an assembly manifest.) when trying to load the assembly. I use the same DLL, what could the problem be?