How do I serialise Lambdas and Event delegates when Tombstoning on the Windows Phone 7?

Question

I've been using the Game State Management sample which has worked so far. I've hit a snag though: when Tombstoning, the screens are serialised; the only trouble is, the MessageBoxScreen has event handlers for Accepted and Cancelled.

What's the best way to serialise these? I did a bit of research on using Expression Trees but this seemed overly complex for what I wanted to do.

How do you serialise these? Or... What alternative approach do you use to save the state of a screen that contains delegates?