The project file is missing the 'subsection' sub-section of the 'section' section
The SubSection (subsection) is Include and section (section) is Files.
This error is most likely caused by editing the project file by hand.
To correct this error
- Work in Show All Files mode (by clicking that button in the Solution Explorer toolbar) and include relevant files.
If you get this error, the project will open, but no files will be added to the project.