Recently when creating a new BizTalk 2009 Orchestration I encountered a build error that I have not previously encountered. The Orchestration build error given was: Preprocessor directive must appear as the first token on a line After a small amount of investigation I discovered that the cause of this error was the Filter Expression that I had applied to the receive shape in my Orchestration. I had put: BTS.MessageType == http://targetnamespace#root... This should have been: BTS.MessageType == "http://targetnamespace#roo... ......