In order to get to the bottom of an error I was having in my controller, I created my own ExceptionFilterAttribute and registered it for the controller (as described here: http://weblogs.asp.net/fredriknormen/asp-net-web-api-exception-handling -
I'm using the ExceptionHandlingAttribute class posted there).
Now, if something goes wrong in a controller method, I do get the OnException in my ExceptionFilterAttribute. And then, when I get to the code where the custom error is returned
throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content = new StringContent("An error occurred, please try again or contact the administrator."),
ReasonPhrase = "Critical Exception"
});
Visual studio catches this and informs me that there's an HttpResponseException that's not handled by user code.
Of course there is.. this thing is supposed to go to the client.
Shouldn't this not pop up as throwing the HttpResponseException at this point is how you're supposed to return something to the client?
But this means decorating all your data objects with an error which may not always be possible - and isn't one point of using rest that you use the HTTP response codes to tell whomever is using your controller something about the error? E.g. if I don't find
a customer (to take your example), in my case, I'd return an http 404 since tthe customer with id so and cannot be found. And I do similar things for adding customers (e.g. duplicate objects). It also means whomever is calling a method on your controller has
to look at the response object and its error message to determine if the call was successful or not. I much rather tell the caller immediately with an http response code that something wasn't working out (and that's how thirdparty rest apis I'm using do things).
In any way - my ExceptionFilter is meant to only catch uncaught exceptions and return something more meaningful than just an HTTP 500 (so I'm using it as suggested). I'm just wondering why visual studio is catching those. It is rather similar than the issue
I have with async vs. sync controller methods returning an HttpResponseException.. in async, things work as expected, in sync, visual studio catches the exception. So there seems to be some kind of logic behind that I'm trying to understand.
Instead of throwing exception, try following solution. You are not seeing exceptions in Async method because of the difference in exception handling in Async methods.
public HttpResponseMessage GetProduct(int id)
{
Product item = repository.Get(id);
if (item == null)
{
var message = string.Format("Product with id = {0} not found", id);
return Request.CreateErrorResponse(HttpStatusCode.NotFound, message);
}
else
{
return Request.CreateResponse(HttpStatusCode.OK, item);
}
}
When you run application from Visual Studio and if there any unhandled exception or any explicitly thrown exception like HttpResponseException in your case, Visual Studio will break. This is the default behavior of Visual Studio in different type of applications
like windows app, console app or web. This will happen only when you run application from Visual Studio. If you enter rest url in browser after hosting in IIS, then your unhandled exception handler (Exception filter) will catch this exception.
None
0 Points
22 Posts
ExceptionFilterAttribute - returned HttpResponseException is caught by visual studio
Apr 09, 2015 09:26 AM|stephan.steiner|LINK
Hi
In order to get to the bottom of an error I was having in my controller, I created my own ExceptionFilterAttribute and registered it for the controller (as described here: http://weblogs.asp.net/fredriknormen/asp-net-web-api-exception-handling - I'm using the ExceptionHandlingAttribute class posted there).
Now, if something goes wrong in a controller method, I do get the OnException in my ExceptionFilterAttribute. And then, when I get to the code where the custom error is returned
throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.InternalServerError) { Content = new StringContent("An error occurred, please try again or contact the administrator."), ReasonPhrase = "Critical Exception" });Visual studio catches this and informs me that there's an HttpResponseException that's not handled by user code.
Of course there is.. this thing is supposed to go to the client.
Shouldn't this not pop up as throwing the HttpResponseException at this point is how you're supposed to return something to the client?
Contributor
2290 Points
493 Posts
Re: ExceptionFilterAttribute - returned HttpResponseException is caught by visual studio
Apr 09, 2015 08:19 PM|santhoshje|LINK
I would prefer handling exception in controller if possible and send custom error message. Let exception filter to handle any unhandled exception
You can try like this
Controller
public class CustomerController : ApiController { public Customer Get(int? id) { Customer customer = new Customer(); try { if (id.Value > 0) { // Get Cutomer details return customer; } else { customer.ErrorMessage = "Invalid id"; } } catch (Exception ex) { customer.ErrorMessage = "Custom error message"; //customer.ErrorMessage = ex.Message; }return customer;
} }
Model class
public class Customer { public int CustomerId { get; set; } public string Name { get; set; } public string ErrorMessage { get; set; } }None
0 Points
22 Posts
Re: ExceptionFilterAttribute - returned HttpResponseException is caught by visual studio
Apr 10, 2015 12:34 PM|stephan.steiner|LINK
Hi
But this means decorating all your data objects with an error which may not always be possible - and isn't one point of using rest that you use the HTTP response codes to tell whomever is using your controller something about the error? E.g. if I don't find a customer (to take your example), in my case, I'd return an http 404 since tthe customer with id so and cannot be found. And I do similar things for adding customers (e.g. duplicate objects). It also means whomever is calling a method on your controller has to look at the response object and its error message to determine if the call was successful or not. I much rather tell the caller immediately with an http response code that something wasn't working out (and that's how thirdparty rest apis I'm using do things).
In any way - my ExceptionFilter is meant to only catch uncaught exceptions and return something more meaningful than just an HTTP 500 (so I'm using it as suggested). I'm just wondering why visual studio is catching those. It is rather similar than the issue I have with async vs. sync controller methods returning an HttpResponseException.. in async, things work as expected, in sync, visual studio catches the exception. So there seems to be some kind of logic behind that I'm trying to understand.
Contributor
2290 Points
493 Posts
Re: ExceptionFilterAttribute - returned HttpResponseException is caught by visual studio
Apr 10, 2015 07:49 PM|santhoshje|LINK
Instead of throwing exception, try following solution. You are not seeing exceptions in Async method because of the difference in exception handling in Async methods.
public HttpResponseMessage GetProduct(int id) { Product item = repository.Get(id); if (item == null) { var message = string.Format("Product with id = {0} not found", id); return Request.CreateErrorResponse(HttpStatusCode.NotFound, message); } else { return Request.CreateResponse(HttpStatusCode.OK, item); } }Contributor
2487 Points
687 Posts
MVP
Re: ExceptionFilterAttribute - returned HttpResponseException is caught by visual studio
Apr 12, 2015 04:32 AM|damienBod|LINK
Web API provides an IExceptionHandler. Implement this and handle your exceptions as required.
https://damienbod.wordpress.com/2014/02/12/exploring-web-api-exception-handling/
greetings Damien
Contributor
2290 Points
493 Posts
Re: ExceptionFilterAttribute - returned HttpResponseException is caught by visual studio
Apr 12, 2015 11:21 PM|santhoshje|LINK
When you run application from Visual Studio and if there any unhandled exception or any explicitly thrown exception like HttpResponseException in your case, Visual Studio will break. This is the default behavior of Visual Studio in different type of applications like windows app, console app or web. This will happen only when you run application from Visual Studio. If you enter rest url in browser after hosting in IIS, then your unhandled exception handler (Exception filter) will catch this exception.
In case of Asyc methods, visual studio is not breaking because of the difference in exception handling Async methods (https://msdn.microsoft.com/en-us/magazine/jj991977.aspx).