If you download GTK# and using RH 8.0 you will haved trouble compile#. Two errors will occur- 1. change the link for install-sh and mkinstalldirs (not sure about the last one) to the correct location.
2. run the last make install as root.
3. run lnconfig before attempting to compile
4. make sure to add the dll.
5. use mcs -lib:/usr/local/lib -r gtk-sharp.dll -r glib-sharp.dll filename.cs (to compile)
Hope this helps.

John