[Gtk-sharp-list] Synchronisation of menu items and toolbar buttons with app state

[vanosten]

Hi

I would like to synchronize the state of the menu items, toolbar 
buttons, etc. with the state of my application (e.g. inactivate when 
command is unavailable). This must have been solved a thousand times. I 
can also come up with my own solution, which I implemented for a few 
buttons. But: there must be more intelligent/generaliyable ways to do this:
# Can someone point me to some docs of patterns/solutions? Documents 
like the HIG tell you what to do, but not how :-(
# Is there something in GTK+/GTK# that makes this task easier?

Thank you very much ... Rick