Mixing MVC and Web API Error Handling - asp.net-mvc-4

Question

We have an MVC 4 web application where we use the web.config file to handle custom errors.
<system.webServer>
<validation validateIntegratedModeConfiguration="false" />
<httpErrors errorMode="Custom" existingResponse="Replace">
<remove statusCode="403" />
<error statusCode="403" responseMode="ExecuteURL" path="/Error/AccessDenied" />
<remove statusCode="404" />
<error statusCode="404" responseMode="ExecuteURL" path="/Error/NotFound" />
<remove statusCode="500" />
<error statusCode="500" responseMode="ExecuteURL" path="/Error/ApplicationError" />
</httpErrors>
</system.webServer>
All ,of which works as expected.
We are now beginning to implement some new features in this project using AngularJS and Web API. In our Web API controller actions, we are consistently returning a HttpResponseMessage to indicate success/failure of the call. For example:
return Request.CreateResponse(HttpStatusCode.BadRequest, result);
The problem (I think!) we are having is that originally MVC error handling is intercepting the BadRequest result (as is reasonable) so that the HttpResponseMessage result data never gets returned to the calling AngularJS method.
What is the best way to handle errors in this mixed (MVC/Web API) environment so that the Web API HttpResponseMessages are not lost?
Thanks.

Answer 1

I am not sure I have found the best solution, but in the end I removed the httpErrors section from the Web.config and built my own error handler in the Global.asax assisted by the following posts:
StackOverflow
PrideParrot
Global.asax
public void Application_Error(Object sender, EventArgs e)
{
var httpContext = ((MvcApplication) sender).Context;
var currentController = "";
var currentAction = "";
var currentRouteData =
RouteTable.Routes.GetRouteData(new HttpContextWrapper(httpContext));
if (currentRouteData != null)
{
if (
!String.IsNullOrEmpty(
currentRouteData.Values["controller"]?.ToString()))
{
currentController = currentRouteData.Values["controller"].ToString();
}
if (!String.IsNullOrEmpty(currentRouteData.Values["action"]?.ToString()))
{
currentAction = currentRouteData.Values["action"].ToString();
}
}
var ex = Server.GetLastError();
var httpEx = ex as HttpException;
var controller = new ErrorController();
var routeData = new RouteData();
var statusCode = httpEx?.GetHttpCode() ?? 500;
string action;
switch (statusCode)
{
case 400:
action = "BadRequest";
break;
case 403:
action = "AccessDenied";
break;
case 404:
action = "NotFound";
break;
default:
action = "Index";
break;
}
httpContext.ClearError();
httpContext.Response.Clear();
httpContext.Response.StatusCode = statusCode;
httpContext.Response.TrySkipIisCustomErrors = true;
if (statusCode >= 500)
{
Server.Transfer("/Error/ServerError.html");
return;
}
routeData.Values["controller"] = "Error";
routeData.Values["action"] = action;
routeData.Values["statusCode"] = statusCode;
controller.ViewData.Model = new HandleErrorInfo(ex, currentController,
currentAction);
((IController) controller).Execute(
new RequestContext(new HttpContextWrapper(httpContext), routeData));
}
My error controller then looked like this:
[AllowAnonymous]
public sealed class ErrorController
: AblController
{
public ActionResult Index(int statusCode)
{
ViewBag.StatusCode = statusCode;
return View("Error");
}
// HTTP 400 - Bad Request
public ActionResult BadRequest()
{
// Now handled by Global.asax - Application_Error
// Response.StatusCode = (int) HttpStatusCode.BadRequest;
// Response.TrySkipIisCustomErrors = true;
if (Request.IsAjaxRequest())
{
return Json(
new
{
error = new ErrorSummary("Bad Request")
});
}
return View();
}
// HTTP 403 - Access Denied
public ActionResult AccessDenied()
{
// Now handled by Global.asax - Application_Error
// Response.StatusCode = (int) HttpStatusCode.Forbidden;
// Response.TrySkipIisCustomErrors = true;
if (Request.IsAjaxRequest())
{
return Json(
new
{
error = new ErrorSummary("Access Denied")
});
}
return View();
}
// HTTP 404 - Not Found
public ActionResult NotFound()
{
// Now handled by Global.asax - Application_Error
// Response.StatusCode = (int) HttpStatusCode.NotFound;
// Response.TrySkipIisCustomErrors = true;
if (Request.IsAjaxRequest())
{
return Json(
new
{
error = new ErrorSummary("Not Found")
});
}
return View();
}
}
}
I also turned the custom error mode off in the Web.config
<customErrors mode="Off" />
This solution needs more testing, but so far it seems to be performing as expected/as required.