Styjun

I'm testing centralized exception handling in my ASPNetCore application and wanted to see if an unexpected exception is thrown it is going to be correctly handled by app.UseExceptionHandler() middleware and logged to a specific logging target. I disconnected the SQL database expecting to see Database.EnsureCreated() method in the DbContext class constructor throwing System.Data.SqlClient.SqlException. The problem is that it does throw such an exception, but it appears locally instead of being handled by centrelized error handler. The final result is that a client never gets a response message explaining what happened with the status code 500.

It seems to be strange as the handler works correctly with an exception which I throw inside controllers.

Here is my centralized exception handler configuration:

app.UseExceptionHandler(appError =>
 
 appError.Run(async context =>
 
 var errorFeature = context.Features.Get<IExceptionHandlerFeature>();

 if (errorFeature != null)
 
 var exception = errorFeature.Error; 

 logger.LogError(exception.ToString());

 await context.Response.WriteAsync("An unexpected error occurred! Try again later");

 

 );
 ); 

Could anyone tell me give me a hint on what I might be doing wrong? Has anyone come across a similar problem?

Your code looks fine to me. What you are experiencing is a First-Chance-Exception. This means that an exception has been thrown that might eventually get handled. During runtime your ExceptionHandler should perfectly handle your exception.

At debugging time however, Visual Studio breaks for that exception. The behaviour of Visual Studio can be configured in the Exception Settings (Debug > Windows > Exception Settings). See Microsoft Docs for more information on that.

So what you basically have to do is to tell Visual Studio to continue debugging on a SqlException

You can use own middleware to handle exception as first-person

public class ExceptionFilter: IExceptionFilter

 public void OnException(ExceptionContext context)
 
 String message = String.Empty;

 Type exceptionType = context.Exception.GetType();
 if (exceptionType == typeof(NotImplementedException))
 
 message = "A server error occurred.";
 context.HttpContext.Response.StatusCode = (int)HttpStatusCode.NotImplemented;
 context.Result = new RedirectResult("/Home/Index");
 
 else if (exceptionType == typeof(AppException))
 
 message = context.Exception.ToString();
 context.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError;
 context.Result = new RedirectResult("/Home/Index");
 
 //HttpResponse response = context.HttpContext.Response;
 //response.StatusCode = (int)status;
 //context.Result = new RedirectResult("/Home/Index");
 

And in your Startup.cs

app.UseMiddleware(typeof(ExceptionFilter));