Mef Core is a lightweight and extensible implementation of the.NET MEF (Model-Driven Framework) specification. So in your application, you use a Constructor selection logic, specifying which contracts the framework should import. In our case, we have some UI services which do not provide a UI, but want a global notification icon. We will also implement the Mef observable interfaces for automatic property change notification. This is specific to the AppServicePlugin Framework, but you might be