Debugging .Net web api

I built a .net web app using visual studio. I tested it in visual studio and it seemed to work fine. After publishing it locally and copying to my remote web server it seems to keep crashing the application pool and I'm not sure how to debug it.

How I published it: I published it locally and copied all the files to: wwwroot/ss/ on the remote server. After that, I installed the folder as an application in IIS. Because it was built using version .net 4.5 framework but I only had .net 4.0 application pools I did:

appcmd set apppool /apppool.name: api /managedRuntimeVersion:4.5

Now, anytime I go to the application using my url: mywebsite.com/ss/api/controller/param, I get a 503 service unavailable.

When I check the application pool after I go to that URL, the app pool has been shut down. I tried using try/catches, but it doesn't seem to help. All I see in the log file is:

2015-03-09 01:01:39 remoteIP 14132 siteIP 80 HTTP/1.1 GET /ss/api/controller/param 503 4 AppOffline api

What's the best way to debug this? Can I use a remote debugger? Is there any folder besides C:\Windows\System32\LogFiles\HTTPERR or logs/LogFiles folder in the site root where I can find more information about why it crashed?

EDIT: If it is at all useful, I see in the event log:

I see several warnings: A process serving application pool 'api' terminated unexpectedly. The process id was '2724'. The process exit code was '0xfffffffe'.

followed by: Application pool 'api' is being automatically disabled due to a series of failures in the process(es) serving that application pool.

There is no such thing as the .net 4.5 run time. Set it back to .net 4.0

appcmd set apppool /apppool.name: api /managedRuntimeVersion:4.0

Fun fact.

There are only 3 .net runtimes as of 2015-03-09

• .net runtime 1.0
• .net runtime 2.0
• .net runtime 4.0

These runtimes allow you to run the following (ignoring the various SP)

• .net runtime 1.0
  • .net framework 1.0
• .net runtime 2.0
  • .net framework 2.0
  • .net framework 3.0
  • .net framework 3.5
• .net runtime 4.0
  • .net framework 4.0
  • .net framework 4.5
  • .net framework 4.5.1
  • .net framework 4.5.2