I'm running an ASP.NET 4.0 web application on IIS6 (Windows Server 2003 x64). This app is one of many running on this server under the Default Web Site -- but is alone on it's own application pool because the other sites are all running ASP.NET 2.0 still.

When I deploy my application, it works just fine until the application pool recycles or kills its worker process (by default 2 hours or 20 minutes with no activity). After this, I get the error: "Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.

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

Refreshing the page, recycling the application pool, and iisreset do nothing. But, I can bring the site back online again for a little while by simply redeploying it.

The stack trace seems to start at an EntityDataSource -- see below:

[ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.]
   System.Reflection.RuntimeModule.GetTypes(RuntimeModule module) +0
   System.Reflection.Assembly.GetTypes() +144
   System.Data.Metadata.Edm.ObjectItemConventionAssemblyLoader.LoadTypesFromAssembly() +45
   System.Data.Metadata.Edm.ObjectItemAssemblyLoader.Load() +34
   System.Data.Metadata.Edm.AssemblyCache.LoadAssembly(Assembly assembly, Boolean loadReferencedAssemblies, ObjectItemLoadingSessionData loadingData) +130
   System.Data.Metadata.Edm.AssemblyCache.LoadAssembly(Assembly assembly, Boolean loadReferencedAssemblies, KnownAssembliesSet knownAssemblies, EdmItemCollection edmItemCollection, Action`1 logLoadMessage, Object& loaderCookie, Dictionary`2& typesInLoading, List`1& errors) +248
   System.Data.Metadata.Edm.ObjectItemCollection.LoadAssemblyFromCache(ObjectItemCollection objectItemCollection, Assembly assembly, Boolean loadReferencedAssemblies, EdmItemCollection edmItemCollection, Action`1 logLoadMessage) +580
   System.Data.Metadata.Edm.ObjectItemCollection.ExplicitLoadFromAssembly(Assembly assembly, EdmItemCollection edmItemCollection, Action`1 logLoadMessage) +193
   System.Data.Metadata.Edm.MetadataWorkspace.ExplicitLoadFromAssembly(Assembly assembly, ObjectItemCollection collection, Action`1 logLoadMessage) +140
   System.Web.UI.WebControls.EntityDataSourceView.ConstructContext() +756
   System.Web.UI.WebControls.EntityDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +147

This is a bug filed for the same (or similar) problem: http://connect.microsoft.com/VisualStudio/feedback/details/541962/unable-to-load-one-or-more-of-the-requested-types-connected-with-entitydatasource

Question: Has anyone seen this and have advice? I've tried copy-local on all the references... Works just fine on my dev machine. Works on the server until the application pool worker process recycles. I'm building in release mode, but experience the same result when I build for debug. I'm stumped.