Ok...So I have something really fricken annoying going on.
Timeline:
(Visual Studio 2012)
9pm - Have a WPF solution open I downloaded from codeplex. Compiles Perfect. I can open the MainWindow.xaml and see it in the designer just fine.
9:45 - Done so I close it.
10pm - Open it back up. Double click MainWindow.xaml. "INVALID MARKUP". The project references MahApps.Metro. Telling me MetroWindow isnt valid in namespace as well as several other things that were just working fine 45 minutes ago.
10-2am - I try re-building, cleaning re-building, deleting shadowcache, reset usersettings, delete bin/obj folders. Sometimes the only thing that works, is deleting or reinstalling (via nuget) the reference its yelling at me about. Nothing works.
Literally since then, EVERY project that worked just fine just hours before, now I cant view it in the designer, Even thoguh they compile JUST fine. Every single one says "invalid markup". I cant understand this.
-Current: Uninstalled VS 2012 and installed VS 2013. No change. PLEASE HELP
-Josh