I got this error today in a BizTalk orchestration: “Identifier “abc” does not exist in ‘global_NS.AppName”; are you missing an assembly reference?” Basically, the auto-complete (Intellisense) wasn’t giving my .BizTalkComponents namespace after I typed in “AppName.”. So I typed it in anyway, and pressed CNTL-Space-Bar, and that’s when the error occured.

I had typed in AppName.BizTalkComponents, which was a valid namespace in C# program, to which I had made a project reference.

Normally, I follow naming conventions that match the BizTalk Deployment Framework, but in this case, I has an old application, written by a predecessor. I use a Find/Replace Utility to replace the namespace from NewAppname to Appname.
So, the namespace of the orchestration itself was Appname. I should have named it Appname.BizTalk or something similar.

So to fix the issue, I overrode the namespace of the orchestration to Appname to Appname.BizTalk (as shown below):