So this problem now happened to me for the fourth time. I was just writting in VS minding my own business, when an erro popped up saying something like: The file has been changed outside of the environment. You have to reaload the solution. And so I did, but after that all of the projects under my solution explorer dissappeared, and the size of the .sln file changed to 1kb. Now today, the same thing happened, but the error was diffrent and popped up when I clicked build, saying something:Cmake hs generated 3 .sln files and I clicked reload, after that it gave me one more error and after that all of the projects under solution explorer dissappeared. I am starting to get preety frusrated... Seriously Microsoft...
EDIT: Just to get everything clear, I am using Microsoft Visual Studio 2010, and was writing in c++.
Something's clearly deleting the files while you're in Visual Studio. Are you on a network drive? Maybe you should use the File Explorer to monitor what's going on.