- cherry-picked from 1a241fcfc2f8 in 'master' branch
- avoid new CS1504 errors because compiler can't find the ErrorPage.cshtml file
- we override Arcade's `$(MicrosoftCodeAnalysisCSharpVersion)`
- use new option in GeneratePage.ps1 script
- script also did not know `RazorSyntaxGenerator` had moved to this repo
- reflect latest `RazorSyntaxGenerator` processing
- run GeneratePage.ps1
- update README.md
nits:
- quote all paths in GeneratePage.ps1 script
- remove passive voice in README.md
* fix#12516 by cleaning up error page
* add a Diagnostics.slnf because I was there
* missed the IIS update
* update WebHost's error page
* Fix slnf path
Doug Bunting
Kevin Pilch
Andrew Stanton-Nurse