Given a C# 2005 Web Service project, can the web service respond to Events?

Similar to a VB.NET Windows application might instantiate an ActiveX Objects, via "Dim WithEvents"?

I have a way for a client of the webservice to subscribe to an *Async callback.

However the webservice seems to be more-or-less idle when not being called to do something.

How can I make the webservice "wake itself up" to an extrenal event?

I presume delegates would enter the picture...

Thanks!