I had the same problem, but for me even rebooting VS did not work. I even tried restarting the PC and uninstalling the recently installed programs. nothing helped.
The actual problem in my case was,
I could edit .cs files, but I could not edit xaml files. Only I could add line breaks in xaml. I spent many hours and finally found that the problem was with Jetbrains Resharper.
I installed Resharper a few days ago, and after using the rating, I suspended the license to use the rating effectively. (In the resharper menu, you have the option to allow pause). So, when the evaluation is suspended, I could not edit xaml fils, and in the end I had to resume the evaluation or remove the restart completely.
IMO is unfair with Jetbrains.
Chandru
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