ASP.NET Core startup exceptions handling

Question

When the code in the startup class throws, ASP.NET Core catches the exception instead of letting it fall through behind the IWebHost.Build call.

The app consequently does start but only serves an error page.

So how do I react to a problematic startup if I don't get to catch the exception myself?

Please don't tell me I need to catch it in Startup.cs.

You can follow this [pattern](https://stackoverflow.com/a/38935583/7177029) — Kunal Mukherjee, Mar 28 '19 at 13:12
Where is the exception being thrown in the `ConfigureServices()` or `Configure()` — Kunal Mukherjee, Mar 28 '19 at 13:14
`ConfigureServices` for now, but really the problem arises for both. — John, Mar 28 '19 at 13:15
Can you chain the `CaptureStartupErrors()` method to `IWebHost.Build()` call in `Program.cs` like this: `WebHost.CreateDefaultBuilder(args).CaptureStartupErrors(false)` — Kunal Mukherjee, Mar 28 '19 at 13:22
@John Better you can log the exception to a text file. Is there any problem of doing so? — TanvirArjel, Mar 28 '19 at 13:25
Technically, this is something that belongs in your CI/CD pipeline. If you had even a single integration test, you'd fail before you made it to release. — Chris Pratt, Mar 28 '19 at 13:28
@TanvirArjel Yes, ASP.NET Core doesn't tell me that there was an exception. So I can't react and log anything. — John, Mar 28 '19 at 13:31
@ChrisPratt It can also fail because the configuration changed. — John, Mar 28 '19 at 13:35
Essentially, the point is that try/catch is all you've got. An ASP.NET Core app is just a console app with a lot of functionality plugged in. However, at the level of `Program.cs` and even `Startup.cs`, you're still at a very basic console app level. There's no grand exception handling middleware goodness and such, yet. — Chris Pratt, Mar 28 '19 at 13:35
The configuration is *also* supposed to be part of your CI/CD pipeline. — Chris Pratt, Mar 28 '19 at 13:35
@ChrisPratt And ASP.NET shouldn't just swallow exceptions in `IWebHost.Build` when it insists to have my startup code to be in a class that it calls. I don't want anything fancy, I want the exception to fall through. — John, Mar 28 '19 at 13:38

score 0 · Answer 1 · answered Aug 18 '21 at 19:58

0

Essence of the comment thread above: do not call

builder.CaptureStartupErrors(true)

in your Program.CreateWebHostBuilder method.

answered Aug 18 '21 at 19:58

Marc Wittke

2,991
2
30
45

ASP.NET Core startup exceptions handling

1 Answers1