While working with EDI messages in Orchestrations you might get the following error message.
Identifier ‘EDI’ doesn't exist in ‘Orchestration’; are you missing an assembly reference?
This happens when you try to access the EDI properties of a message in an orchestration like EDI.ISA06
To resolve this issue ensure the Orchestration Project has a reference to the assembly Microsoft.BizTalk.Edi.BaseArtifacts.dll
It is located in the folder you installed BizTalk Server ( C:\Program Files (x86)\Microsoft BizTalk Server 2010\ )