why does visual studio delete my classes when I update entity framework model

Question

I\'m having a strange problem when I update my EF model (ver 5). It deletes all of the classes that belong to that model.

My situation was like this. I changed the key

Answer 1

It's been a long while, but in the end it turned out I had some errors in my edmx file which I hadn't seen, and that was causing the poco class files to not be generated.