ASP.NET Core 2.0 site POST request resulting in 404 on Azure

Question

I've just upgraded an ASP.NET Core 1.1 web application to 2.0 and tested without issue locally. However, when the site is deployed to Azure a POST request that worked locally results in a 404 (I guess this could be the same for all POST requests, but I'm unable to log-in due to the issue).

Any ideas why this might fail to be working when deployed to Azure but working perfectly when run through IIS Express locally?

I deleted the original deployment slot on Azure and re-created as initially deploying over the slot mixed old 1.1 DLL's with the newer 2.0 DLL's and prevented the site working at all.

Have tried activating logging? Maybe you can get some clues there? — Alex Albu
@AlexAlbu thanks, that's where I found the real issue. Just need to work out why I was receiving a 4040 instead of an error response code! — Gavin

Gavin Gavin · Accepted Answer · 2017-09-18T09:20:42

Seems I was caught out by poor handling of errors by my web application. I'd assumed that app.UseExceptionHandler("/Error") (I default my HomeController to not require the leading "Home" for /Home/Error) in Startup.cs would redirect to an error page, but for me it is not.

My underlying issue was a database connection error that caused the POST controller method to fail. I was caught out by the response returning a 404 rather than an error status.

I will need to investigate how error handling works in more detail for ASP.NET Core it seems.

ASP.NET Core 2.0 site POST request resulting in 404 on Azure

1 Answers