A nice feature to use when cleaning up old solutions would be to see which files that isn't in the solution. Could be in the Open File in Solution dialog.
I don't understand. One answer is most files on your entire hard drive, since most of them are not part of the solution.
If you are only talking about header files that are included with a #include statement into one of the files in your solution then try compiling the solution. The compiler has to be able to find ever one of these files, so the files are either part of the solution, or in a well defined directory.
If the files are not in the solution then VA may not know about them, it uses the same information as the compiler / IDE to locate files.
I believe the request is to locate files that exist in the solution directory and its subdirectories that are not included in the solution itself, ignoring .obj and other temporary or build-related files.
Kevin Sikes Infotainment Platform Design Engineer Ford Motor Company