New Post: Resolver assembly file plug-ins in System.Composition (a la DirectoryCatalog)

(I'll refer to System.ComponentModel.Composition as .net 4.5 MEF and System.Composition as Windows Store Apps MEF)

I am using System.Composition with Web Api.

Besides the referenced types in the host project I want to discover some contract enforcing plug-ins in a folder.

How can I accomplish it with System.Composition?

Do I need to bridge it with System.ComponentModel.Composition? And If so will it hurt my performance?

I have used System.Composition since it seems a lightweight version for Windows Store and Web Apps. Should I just stick with System.ComponentModel.Composition?

Thanks.