"Could not load file or assembly System.Web.Http.WebHost, Version=126.96.36.199".
Came to work one morning, built my system, WTF, error as above.
All worked perfectly when I left the day before.
There had been a Windows Update during the night and obviously some dll's had been updated - so much for backward compatibility.
Problem was - I couldn't figure out who was calling this dll and hence where the reference / binding was
Mr. Google and came across this Scott Hansleman post:
Back to Basics: Using Fusion Log Viewer to Debug Obscure Loader Errors
I'm using VS 2013 and Windows 8.1.
So go to:
C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\Tools\Shortcuts
This is the shortcut to the VS Command Line Tool - "Developer Command Prompt for VS2013".
In the command line - fuslogvw.exe - run as Administrator.
In Settings - "Log bind failures to disk" / "Enable custom log path". Type in path - make sure the path exists.
Navigate to your web site - get the error - back to the tool - click "Refresh" - BOOM.
You will also notice that the text on the ASP.NET error page is different - it doesn't talk about the regedit change.
To repeat - if you use the tool you don't have to screw around with registry settings.
When you are done, remember to disable the log via the tool as it slows everything down.