Why is Visual Studio 2008 always rebuilding my whole project?

Question

I have a Visual Studio project with about 60 C++ source files. I can do a build, and it completes without errors. But if I immediately hit F7 again, it always re-compiles about

Answer 1

In my case I changed system data time to previous date so it is rebuilding every time because of different time stamp of the files once changed to the current time its not rebuilding every time.