MVC 4 MEF: System.TypeLoadException: Inheritance security rules violated by type: 'DotNetOpenAuth.Messaging.OutgoingWebResponseActionResult'

Question

What causes this error?

System.TypeLoadException: Inheritance security rules violated by type: 'DotNetOpenAuth.Messaging.OutgoingWebResponseActionResult'. Derived types must either match the security accessibility of the base type or be less accessible.

I got this error on my MEF initiator which reads plugins from folder and try to assembly it to the main apps.

Here is my code:

public class Bootstrapper
{
    private static CompositionContainer CompositionContainer;
    private static bool IsLoaded = false;

    public static void Compose(List<string> pluginFolders)
    {
        if (IsLoaded) return;

        AggregateCatalog catalog = new AggregateCatalog();

        catalog.Catalogs.Add(new DirectoryCatalog(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"),"*"));

        foreach (string plugin in pluginFolders)
        {
            DirectoryCatalog directoryCatalog = new DirectoryCatalog(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Modules", plugin), "*");
            catalog.Catalogs.Add(directoryCatalog);
        }

        CompositionContainer = new CompositionContainer(catalog);

        CompositionContainer.ComposeParts();
        IsLoaded = true;
    }
}

I got the error when trying to debug this:

catalog.Catalogs.Add(new DirectoryCatalog(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "bin"),"*"));

and this:

DirectoryCatalog directoryCatalog = new DirectoryCatalog(Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Modules", plugin), "*");
catalog.Catalogs.Add(directoryCatalog);

When i debug the code, catalog.Parts has this error:

new System.ComponentModel.Composition.Primitives.ComposablePartCatalogDebuggerProxy(catalog)).Parts 'Threw an exception of type 'System.Refrection.ReflectionTypeLoadException'

and the catalog.Parts.LoaderException produce error:

System.TypeLoadException: Inheritance security rules violated by type: 'DotNetOpenAuth.Messaging.OutgoingWebResponseActionResult'. Derived types must either match the security accessibility of the base type or be less accessible.

I am guessing that there is security error that prevents the system to assembly the plugin from another folder.

My plugin folder is in:

RootAppFolder
---- Modules
-------- PluginFolder <-- Here

I am now building an MVC 4 CMS that can load plugins on runtime. So i just need to copy the plugin to Modules folder. I am following this guide to achieve my pluggable module structure.