ASP.Net Core UseExceptionHandler not handling all exceptions?

Question

I have an ASP.Net Core 2 web api project. I have added the following to the Configure method in my Startup.cs file app.UseExceptionHandler();

I noticed in my Postman tests that I was getting an "Unable to get response" result. Server-side logging shows that the error has to do with Tables being missing from my Database. Which is fine, I can resolve that. But my question is why would the server not be returning a 500 Internal Server Error? Why is it dying, and returning no response at all to Postman?

So, in my Controller, I purposely throw an Exception to test the handler, and call the URL from Postman, and indeed, I get back a 500 Internal server error response, as expected.

Why are the "deeper down" errors being thrown from EFCore not being handled by the ExceptionHandler middleware, and crashing my app? Am I missing something?

Answer 1

In your startup.cs, move the UseMvc() tag to the bottom of the pipeline i.e.

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
  ...
  app.UseExceptionHandler();
  app.UseMvcWithDefaultRoute(); 
}

In my case, the request pipeline faulted on startup when the route launched by the browser did not exist. In that scenario, my app.UseExceptionHandler() before the app.UseMvc() was not executed.