Found at http://connect.microsoft.com/VisualStudio/feedback/details/541962/unable-to-load-one-or-more-of-the-requested-types-connected-with-entitydatasource in the mist of the discussion, adding this code to the application allows to see the details of the exception:
foreach (var asm in
This is quite useful because otherwise you get the exception as this text in the browser (IE) trying to load the page:
[ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.]
Except that of course in the browser you can’t look the LoaderExceptions property, thus the need to repro under a debugger.