Visual Studio 2013 Can't save, build, or rebuild solution

Question

Suddenly after i clicked clean solution i am no longer able either to save, build or do anything to the solution. It appears to be a bug as every time i hit CTRL+S or just Rebuild or Build or even Start button i get this message

• Also i double checked all the assemblies and they are there nothing is missing. I need to find a solution without losing my unsaved data.

Answer 1

Well this is strange glitch which I once faced with Visual Studio which results in losing the linkage to it's references or something like that.

A quick fix would be just

1. Opening the project in a 2nd visual studio instance (without
   closing the existing one to keep your data alive!)
2. Rebuild your project from the newly opened 2nd instance then close
   and return to your bugged visual studio (1st instance) and it should work be able to save/build/rebuild now.
3. When switching back to your 1st instance, if you had made changes
   in the 2nd instance to get your project to compile, the 1st instance will detect these and ask if you would like to reload the changed
   files. Select "No to all" otherwise you will lose your unsaved
   changes in the 1st instance.