Asp.Net 5/Core app.UseExceptionHandler() not working

Question

I have in startup

(UPDATE: the solution was to move UseRouting under the /api/error routes)

app.UseRouting();

if (env.IsDevelopment()) {               
    app.UseExceptionHandler("/api/error/error-local-development"); 
    SwaggerConfig.Configure(app);              
}
else {             
    app.UseExceptionHandler("/api/error/error");
}

 app.UseCors();
 app.UseHttpsRedirection();
 app.UseDefaultFiles();
 app.UseSpaStaticFiles(); 
 app.UseAuthentication();
 app.UseAuthorization();
 app.UseRequestLocalization(options);
  app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
                endpoints.MapHub<ResultHub>("/hubs/resultHub");
            });


            app.UseSpa(spa =>
            {
                spa.Options.SourcePath = "wwwroot";
            });

But when throw new Exception() in a controller action, the Error controller Methods are never called.

[Route("api/error")]
[ApiController]
[ApiExplorerSettings(IgnoreApi = true)]
public class ErrorController : OwnBaseController
{
    public ErrorController(IApplicationUserService applicationUserService, ILogger<ErrorController> logger, IDiagnosticContext diagnosticContext) : base(applicationUserService, logger, diagnosticContext)
    {
    }

    [Route("error")]
    public IActionResult Error()
    {
        return Problem(); 
    }

    [Route("error-local-development")]
    public IActionResult ErrorLocalDevelopment([FromServices] IWebHostEnvironment webHostEnvironment)
    {
       var context = HttpContext.Features.Get<IExceptionHandlerFeature>();
       return Problem(
            detail: context.Error.StackTrace,
            title: context.Error.Message);
    }
}

What will happen then? I mean is the app crashes or do the exception appears in the log? or xyz? — Peter Csala, Feb 26 '21 at 14:34
In debug modus i see on the manual "throw exception" serilog logging "an exception of type xx occured in xxx.dll but was not handled in user code", it then jumps to the lines line of my testmethod of my test controller and returns a 500. — edelwater, Feb 26 '21 at 14:40
Where did you put the `UseExceptionHandler` calls before or after the `UseRouting` and `UseEndpoints`? — Peter Csala, Feb 26 '21 at 14:48
Please try to register them before. These could be the very first method calls in the `Configure`. — Peter Csala, Feb 26 '21 at 14:59

Peter Csala · Accepted Answer · 2022-05-11T09:28:46.383

11

It might seem strange but ordering matters.

UseExceptionHandler and UseRouting are both registering middlewares under the hood.

The firstly registered will be the outer most middleware. So if the inner throws exception the outer can catch it and can handle (and/or log) it.

Source

MSDN has some warnings about this, for example:

Handle Errors in ASP.NET Core's UseStatusCodePagesWithReExecute section

If an endpoint within the app is specified, create an MVC view or Razor page for the endpoint. Ensure UseStatusCodePagesWithReExecute is placed before UseRouting so the request can be rerouted to the status page.

ASP.NET Core Middleware's Middleware order section

UseExceptionHandler is the first middleware component added to the pipeline. Therefore, the Exception Handler Middleware catches any exceptions that occur in later calls.

edited May 11 '22 at 09:28

answered Feb 26 '21 at 15:25

Peter Csala

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I was really hoping this simple solution would have fixed my case. My called to UseExceptionHandler is called first, but the unhandled exception still does not call the error handling controller. There must be other causes for this issue. – Matthew MacFarland Sep 06 '21 at 20:52
Hi @MatthewMacFarland, could you please share further details in order to be able to help you? (If needed please create a new question and paste here the link) – Peter Csala Sep 07 '21 at 07:15
1

Hi @PeterCsala, Certainly. I will put my details together and post them soon. – Matthew MacFarland Sep 07 '21 at 13:00
2

Hi @PeterCsala, I discovered my problem while getting ready to post details here. I was running in development mode and the call to `app.UseExceptionHandler()` was only active for when `IsDevelopmentMode = false`. Silly mistake. Everything works perfectly now. – Matthew MacFarland Sep 08 '21 at 20:12
Hi @MatthewMacFarland it happens to everyone, no worries. I'm glad that you could solve it on your own. – Peter Csala Sep 08 '21 at 20:25

score 2 · Answer 2 · edited Dec 16 '22 at 07:20

2

It didn't help for me so, I changed this

app.UseExceptionHandler("Home/Error");

to this

app.UseExceptionHandler("/Error");

and aldo added an attribute route on the action

[Route("/Error")]
public IActionResult Error()

edited Dec 16 '22 at 07:20

Peter Csala

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answered Nov 20 '22 at 10:19

miri l.

141
6

score 0 · Answer 3 · answered Apr 28 '23 at 21:41

0

For me it was the route name was not the same as the usEexceptionHandler:

I had

[Route("/errors")]
public IActionResult Error()

and in my program.cs:

app.UseExceptionHandler("/error");

both names must be the same for it to work

answered Apr 28 '23 at 21:41

Mo D Genesis

5,187
1
21
32

Asp.Net 5/Core app.UseExceptionHandler() not working

3 Answers3

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