Visual Studio error “Object reference not set to an instance of an object” after install of ASP.NET and Web Tools 2015

Question

After installing the ASP.NET and Web Tools 2015 (RC1 update 1) I get the following error within ASP.NET MVC 4 projects when opening *.cshtml files:

Answer 1

In the hopes it might narrow things down/help someone, I did an investigatory approach. For me, I initially moved the folder at C:\Users\{user}\AppData\Local\Microsoft\VisualStudio to My Documents and allowed Visual Studio to re-create it by re-launching it. This removed the errors. So I moved everything back, one-by-one, and restarted Visual Studio each time until I discovered the culprits. These folders were fine to move back in:

• 1033 (overwrote the auto-generated copy with old)
• Designer (was in my old copy, not initially re-created when I re-launched VS, copied it back in)
• Extensions (overwrote the auto-generated copy with old)
• ImageLibrary (overwrote the auto-generated copy with old)
• Notifications (overwrote the auto-generated copy with old)
• STemplate (was in my old copy, not initially re-created when I re-launched VS, copied it back in)
• VTC (was in my old copy, not initially re-created when I re-launched VS, copied it back in)

These files were fine to move back in/overwrite the auto-generated ones:

• ApplicationPrivateSettings (was in my old copy, not initially re-created when I re-launched VS)
• ApplicationPrivateSettings.lock (overwrote the auto-generated copy with old)
• vspdmc.lock (overwrote the auto-generated copy with old)

These files were fine to move back in. Each was in my old copy, and not initially re-created when I re-launched VS:

• .NETFramework,Version=v4.0,Set=Framework,Hash=C958D412.dat
• .NETFramework,Version=v4.0,Set=RecentAssemblies,Hash=0.dat
• .NETFramework,Version=v4.5,Set=Extensions,Hash=75EAE334.dat
• .NETFramework,Version=v4.5,Set=Extensions,Hash=497525A2.dat
• .NETFramework,Version=v4.5,Set=Framework,Hash=5AE9A175.dat
• .NETFramework,Version=v4.5.2,Set=Extensions,Hash=24CEEB0D.dat
• .NETFramework,Version=v4.5.2,Set=Extensions,Hash=72AE305.dat
• .NETFramework,Version=v4.5.2,Set=Extensions,Hash=ADF899D7.dat
• .NETFramework,Version=v4.5.2,Set=Framework,Hash=D8E943A2.dat

These caused problems - delete these files and re-launch VS to allow it to re-create them:

• ComponentModelCache - When I overwrote this folder's contents with my old ones (4 files: MS.VS.Default.cache, .catalogs, .err, .external), this gave me all of the errors I had gotten before about not being able to load packages when loading my project, and the "object reference not set to an instance of an object" error when trying to close VS.
• devenv.exe.config - same as ComponentModelCache
• .NETFramework,Version=v4.0,Set=Extensions,Hash=6D09DECC.dat - causes error output from the JavaScript Language Service, complaining of missing js files
• .NETFramework,Version=v4.0,Set=Extensions,Hash=9951BC03.dat - causes error output from the JavaScript Language Service, complaining of missing js files
• .NETFramework,Version=v4.5.2,Set=RecentAssemblies,Hash=0.dat - causes error output from the JavaScript Language Service, complaining of missing js files

These are the errors from those last .NETFramework files (which I do not get if I do not add them back in):

01:10:11.7550: Referenced file 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\JavaScript\References\libhelp.js' not found.
01:10:11.7550: Referenced file 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\JavaScript\References\sitetypesWeb.js' not found.
01:10:11.7550: Referenced file 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\JavaScript\References\domWeb.js' not found.
01:10:11.7550: Referenced file 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\JavaScript\References\underscorefilter.js' not found.
01:10:11.7550: Referenced file 'C:\Program Files (x86)\Microsoft Visual Studio 14.0\JavaScript\References\showPlainComments.js' not found.

I might just need to re-install/repair the JavaScript Language Service plug-in, so it might be un-related. But definitely devenv.exe.config and ComponentModelCache need to go to correct the "object reference not set to an instance of an object" error.