An exception of type 'System.Reflection.ReflectionTypeLoadException' occurred in ProjectVI.Api.dll but was not handled in user code

An exception of type 'System.Reflection.ReflectionTypeLoadException' occurred in ProjectVI.Api.dll but was not handled in user code

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

public SafeDirectoryCatalog(string directory)
{
    var files = Directory.EnumerateFiles(directory, "*.dll", SearchOption.AllDirectories);

    this.catalog = new AggregateCatalog();

    foreach (var file in files)
    {
        try
        {
            var asmCat = new AssemblyCatalog(file);

            ////Force MEF to load the plugin and figure out if there are any exports
            // good assemblies will not throw the RTLE exception and can be added to the catalog
            if (asmCat.Parts.ToList().Count > 0)
            {
                this.catalog.Catalogs.Add(asmCat);
            }
        }
        catch (Exception ex)
        {
            Log.Instance.Error(ex, "@file " + file.ToString());
            if (ex is System.Reflection.ReflectionTypeLoadException)
            {
                var typeLoadException = ex as ReflectionTypeLoadException;
                var loaderExceptions = typeLoadException.LoaderExceptions;
                if (loaderExceptions.Count() > 0)
                {
                    foreach (Exception exc in loaderExceptions)
                    {
                        Log.Instance.Error(exc, "exception");
                    }
                }
            }

            throw ex;
        }
    }
}

[ReflectionTypeLoadException: Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.]
ProjectVI.Api.Install.SafeDirectoryCatalog..ctor(String directory) in C:\ProjectVI\Code\BA\ProjectVI.Api\Install\SafeDirectoryCatalog.cs:67
ProjectVI.Api.Install.MefConfig.Register() in C:\ProjectVI\Code\BA\ProjectVI.Api\Install\MefConfig.cs:28
ProjectVI.Api.WebApiApplication.Application_Start() in C:\ProjectVI\Code\BA\ProjectVI.Api\Global.asax.cs:30

[HttpException (0x80004005): Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.]
System.Web.HttpApplicationFactory.EnsureAppStartCalledForIntegratedMode(HttpContext context, HttpApplication app) +9916673
System.Web.HttpApplication.RegisterEventSubscriptionsWithIIS(IntPtr appContext, HttpContext context, MethodInfo[] handlers) +118
System.Web.HttpApplication.InitSpecial(HttpApplicationState state, MethodInfo[] handlers, IntPtr appContext, HttpContext context) +172
System.Web.HttpApplicationFactory.GetSpecialApplicationInstance(IntPtr appContext, HttpContext context) +336
System.Web.Hosting.PipelineRuntime.InitializeApplication(IntPtr appContext) +296

[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) +9930568
System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +101
System.Web.HttpRuntime.ProcessRequestNotificationPrivate(IIS7WorkerRequest wr, HttpContext context) +254