Callback

Question

Could anyone help how to implement a callback to an object reference outside my scope (windows service). This is the scenario: 1.- Windows service will fire the callback or an event. 2.- Component that consumes a webservice. 3.- Client consumming the web service through the component. The idea is to notify the component that the client needs to do do something and then the component notifies the client. All this is written in C#. Any help to understand this, is greatly apreciated. Regards,