In my project we are using XAP partitioning (using something similar to what Glen Block describes in his article). My main XAP has my menu, then depending on security permissions I download module XAP's that contain modules of application. One of those sections needs a RadRichTextBox. In an effort turn on the spell check feature we added the dll for the dictionary (Telerik.Windows.Documents.Proofing.Dictionaries.En-US) to the module XAP, however the spell check did not work. In a game of trial and error I added it to the main XAP, and everything worked fine. However I don't want to weigh down my main XAP with stuff for one of the modules, that possibly the user will never need. Any ideas if I need to do something special to get MEF to load the spell check dictionary with it is in the module XAP?