There is kind of a good news/bad news situation going on with Crestron Onvif support at the moment.
The good news? ? Crestron has created a Simpl# class to deal with Onvif. ? This should make creating an Onvif control reasonably easy.
The bad news? ?Their toolchain is broken and won't properly link/copy the necessary DLLs, so it is currently dead in the water.