You should really only need to refresh the project if you have added new classes to it, i.e. new Cpp and H files. When you make a change to a source file, VS2015 is still saying that the target is up to date?
You should also be able to try, Open Windows Explorer, go to the directory of the project, and then right click on the Uproject file, in the popup menu should be a menu item of “Generate Visual Studio Project files”, click on that and it should update the SLN for the project etc. Then give the build a try.
Have you made sure that all the project files are in the correct public and private directories?