Visual Studio “Go to definition” disabled or gray out

Question

Visual Studio\'s Go To Definition is disabled and F12 doesn\'t work. Other commands like Alt-F12 may continue working.

Answer 1

I found that I had to remove my TFS mapping: VS 2010 > open Team Explorer > Drill into the team project > double click source control > right click on the team project in the left pane and do "Remove Mapping" > after everything was removed I manually went to the local folder and deleted any lingering files > back in source control explorer I re-mapped to the same local folder and re-pulled all the code. Now the "go to definition" works again.

Not sure why I had to do this...