I had an orchestration from a BizTalk 2010 that had the following code:

vISA06 = msg_EDI_997(EDI.ISA06);
vISA08 = msg_EDI_997(EDI.ISA08);

We were updating and refactoring to 2016. When I put that code in my 2016 orchestration, it got an error. I checked, and the EDI. fields were not showing up in the Intellinsense “drop down”.

The trick is to reference Microsoft.BizTalk.Edi.BaseArtifacts [c:\Program Files (x86)\Microsoft BizTalk Server 2013 R2\Microsoft.BizTalk.Edi.BaseArtifacts.dll] in your project, then it works fine.