Why is IIS failing to start when I try to debug my web application?

Question

Picture the scene... I'm on a new PC. I've installed VS15 and SQL Server Express. I've enabled IIS in Windows features. I've pulled my (previously working) ASP.NET MVC project from Git. I press F5 and am pleased to see that the build succeeds, Firefox starts up and things are looking good.

But then, oh no! The debug session ends abruptly. Firefox eventually times out.

I've found IIS errors in event viewer that match the timings of my attempts. They reference error code "8007007E". When I put that into the Err.exe utility (as per this article), I get the following:

# as an HRESULT: Severity: FAILURE (1), Facility: 0x7, Code 0x7e
# for hex 0x7e / decimal 126 :
  SYSTEM_THREAD_EXCEPTION_NOT_HANDLED                           bugcodes.h
  NMERR_REMOTE_NOT_A_SERVER                                     netmon.h
  SQL_126_severity_15                                           sql_err
# Invalid pseudocolumn '%.*ls'.
  ERROR_MOD_NOT_FOUND                                           winerror.h
# The specified module could not be found.
# 4 matches found for "8007007E"

Which (to me at least) is a bit of a dead-end. I've tried Googling the individual error messages, but can't find anything useful.

I suppose what I'm saying is: help? If anyone has any pointers, I'd be very grateful.

Answer 1

OK sports fans, we have a resolution on this.

Turns out there were a couple of things wrong here:

1. IIS was being called when IIS express would have been more appropriate. Fixed this by disabling IIS.

2. My applicationhost.config had apparently got mangled somehow. Deleting it and recreating my virtual directory (as per this answer) seemed to do the trick.

Hope this is helpful to somebody in the future.