We are using protobuf.net to serialize classes between mobile devices and back end services, but we now need to adjust what is sent back to the client based upon the \'context\'
It is a good question. The patterns currently supported (ShouldSerialize* etc) are borrowed "as is" entirely from the BCL, hence no context - however there is no reason it can't support parameters in the same way that the callbacks do - indeed, for callbacks it supports pretty much any usage (with/without context etc) - so I can't think of a good reason not to support them here to.
You are right t say it isn't supported currently, but it could be - let me know of this would be useful.