The action can't be completed because the file is open in devenv.exe

This is a pretty infuriating problem I faced today with Visual Studio 2015. Restarting my laptop and then deleting the .dll file that gets locked up in this error didn't help. Deleting everything and doing a repull from source control didn't fix the problem either. Typing %temp% at the start bar and then destroying all of the temp files at C:\Users\tom.jaeschke\AppData\Local\Temp didn't make anything better too. Eventually I changed the Solutions Configuration dropdown at the top of Visual Studio in the "Standard" toolbar (Views > Toolbars > Standard) to something other than Debug and the problem went away.