Weird ASP.NET (MVC) error: "Unable to load one or more of the requested types."

Question

Hi, I'm getting weird error and I have no idea how to resolve it. I've got an ASP.NET MVC website which works fine but once I publish it to a server I get:

"Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information."

Stack Trace:

[ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.]
System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +206
System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +188 System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +295 System.Web.HttpApplicationFactory.GetPipelineApplicationInstance(IntPtr appContext, HttpContext context) +56
System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +231

[HttpException (0x80004005): Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.]
System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +8889839
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +85
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +333

I was trying to google some solution but so far have not found anything. The website has quite a lot of references which is most probably the cause of this problem, however I have no idea how to identify the problematic assembly. The website runs on a subdomain, root site is also ASP.NET MVC app.

Answer 1

After some investigation I was able to track the problem to (Fluent) NHibernate. It was not able to initialize itself due to security constraints on the server (read Medium Trust). First I tried to update to latest version hoping it would work in medium trust environment. Then I tried to patch it to work and then I just simply gave up and contacted my hosting provider to raise the trust level for the app.