From what I've discovered, gtk-sharp has been fully depricated by
gtk-sharp2 now and so as maintainer of this package for fedora, can I
ask that it is retired from rawhide and f9?
yes. But you don't need to mention it here :-)
mail fedora-devel about it in case someone else wants to pick it up for
some package/need we don't know about. (IIRC, you already did).
Then follow the instructions on this page: