Having failed to port XML-RPC.NET to run on Mono, I attempted the same with my IndexedBtree class. I built and ran some performance test code which compares IndexedBtree with the .NET classes Hashtable and SortedList. IndexedBtree ran successfully but enumerating SortedList failed with an InvalidCastException being thrown when the object returned from IEnumerator.Current is unboxed to an instance of DictionaryEntry. The same problem occurred on both Linux and Windows which is at least what you would expect for self-contained code.
And I also did some XML-RPC.NET work today, fixing a couple of bugs reported by Drew Marsh and Dmitry Jemerov.