Since updating to b7 c# files when opened via Unity will open in notepad rather than Visual Studio (2017) until a file is edited which forces a refresh in the editor. This then mends the link between Unity and VS. This worked fine in b2.
Also if you make that initial edit in a manually started copy of Visual studio, once you double click a file in Unity it will open a second copy of VS.
In addition to this, some runtime errors seem to break the link again. I also moved some script files to a subfolder and it broke ALL gameobject script links. This is making scripting hell at the moment.
On top of that Attach to process is no longer working either so no debugging. Attach (in the toolbar) briefly appears when VS starts then gets replaced with the regular Start once its loaded. Debug → attach to unity debugger does work but you have to select the Unity instance each time.