Question

So, I have exports decorated with metadata attributes but on the container it seems like the Metadata collection of these parts are empty thus not correctly importing a Lazy collection with metadata.

Any thoughts why this is happening?

Answer 1

Make sure you configure assemblies for MEF to probe inside your Bootstrapper:

protected override void ConfigureAggregateCatalog()
        {
            base.ConfigureAggregateCatalog();

            // Need to add self explicitly, otherwise MEF won't know exports we have here
            this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));

            // Also adding Model project - this is some project that you reference but not Module
            this.AggregateCatalog.Catalogs.Add(new AssemblyCatalog(typeof(Model.ModelService).Assembly));
        }