I just wanted to document here a common error that I still get when I add BTDF to a new project:
MSBUILD : error MSB1009: Project file does not exist.
1. I copied the original solution created by Visual Studio. First you have to have it one level above the project(s) that contain your BizTalk artifacts (schemas, orchs, maps, etc...)
2. In my case, it should not have ".Artifacts" in the name of the solution.
No reply necessary, just sharing this error/solution.