Updating to Visual Studio 2017 15.8.6, now completely broken

Question

I updated to Visual Studio 2017 15.8.6 (I'm running Windows 10, fully up to date) last week and since then I have been completely unable to use Visual Studio.

When I try to create a new Visual C++ project, I get the following errors:

Followed by:

Then:

This is not limited to Visual C++. C# projects also fail:

Even pressing the Help button on the toolbar throws an error:

I spent a long time looking up solutions for these issues and tried a variety of methods:

1) I installed the 'Clear MEF Component Cache' extension and ran that. No luck.

2) I completely removed my VisualStudio folders in my AppData directories. No luck.

3) I re-installed Visual Studio 2017. Twice.

4) I ran a Repair installation.

Nothing works. Re-installing does nothing, and none of the solutions I found on MSDN forums work.

Every project template fails. I ensured every necessary component was selected in the Visual Studio installer. I'm out of ideas.

This is the contents of my ActivityLog.xml file, as referenced in several of the error messages:

[https://pastebin.com/RVgpmDTG][1]

Answer 1

Looks like I found the solution. Ran the following from a VS Developer Command Prompt:

gacutil /u Microsoft.Build.Framework

gacutil /i "C:\Program Files (x86)\Microsoft Visual Studio\2017\Enterprise\MSBuild\15.0\Bin\Microsoft.Build.Framework.dll"