Error Handling for both JsonResult and ActionResult - asp.net-mvc

Question

In ASP.NET MVC 5, I'm trying to extend my site's general Error Handling and I'm having trouble to cover ActionResult and JsonResult in once. I'm aware that JsonResult is divered from ActionResult, but when I return ActionResult I just give MVC a View, and for JsonResult, I handle the result with Javascript.
So the case, where the return value for the Action is an ActionResult, and the Application_Error() returns a JsonResult, the Json with just be printed in the view. What are you supposed to do in that situation? I rather have it to redirect to errorpage or login screen. I don't even know if I'm supossed to craft so javascript that handle the catch of the json to manually redirect or there is some "built-in" MVC mechanisme I should use.
In a simplified example I have the two Action's:
public ActionResult ShowPackages(PackagesViewModel packagesViewModel)
{
var model = PackageBalhelper.GetPackageViewModel(packagesViewModel);
return View(model);
}
[HttpPost]
public JsonResult GetDatatableRows(PackagesViewModel packagesViewModel)
{
var jsonResult = CreateJsonResult(packagesViewModel);
return jsonResult;
}
What I've so far (From MSDN)
protected void Application_Error()
{
HttpContext httpContext = HttpContext.Current;
if (httpContext != null)
{
var requestContext = ((MvcHandler)httpContext.CurrentHandler).RequestContext;
// When the request is ajax the system can automatically handle a mistake with a JSON response. Then overwrites the default response
if (requestContext.HttpContext.Request.IsAjaxRequest())
{
httpContext.Response.Clear();
string controllerName = requestContext.RouteData.GetRequiredString("controller");
IControllerFactory factory = ControllerBuilder.Current.GetControllerFactory();
IController controller = factory.CreateController(requestContext, controllerName);
ControllerContext controllerContext = new ControllerContext(requestContext, (ControllerBase)controller);
var jsonResult = new JsonResult
{
Data = new
{
success = false,
serverError = "500"
},
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
jsonResult.ExecuteResult(controllerContext);
httpContext.Response.End();
}
else
{
LogHelper.WriteMessageToLog("In 'Application_Error'. Not an ajax request'.");
//httpContext.Response.Redirect("~/Error");
}
}
}

Answer 1

What are you supposed to do in that situation? I rather have it to
redirect to errorpage or login screen.
You are on the right track. We definitely do not want to return View (redirect to custom error page), if the client expects Json response from server. Otherwise, it will mess up the client's logic.
This answer might not answer your question directly. However, if you see yourself returning JsonResult a lot, you might want to consider using Web API Controller in ASP.NET MVC 5.
Web API 2.1 supports GlobalExceptionHandler in which you can customize the Http response that is sent when an unhanded application expcetion occurs.
In my case, I use Angular with ASP.NET MVC and Web API. So, I have to return unhandled exception in Json format for Ajax requests.
WebApiExceptionHandler.cs
If your application throws custom exception, you can even filter them here, and return appropriate message.
public class WebApiExceptionHandler : ExceptionHandler
{
public override void Handle(ExceptionHandlerContext context)
{
var exception = context.Exception;
var httpException = exception as HttpException;
if (httpException != null)
{
context.Result = new WebApiErrorResult(context.Request,
(HttpStatusCode) httpException.GetHttpCode(), httpException.Message);
return;
}
/*if (exception is MyCustomException)
{
context.Result = new WebApiErrorResult(context.Request,
HttpStatusCode.NotFound, exception.Message);
return;
}*/
context.Result = new WebApiErrorResult(context.Request,
HttpStatusCode.InternalServerError,
"An error occurred while processing your request.");
}
}
WebApiErrorResult.cs
public class WebApiErrorResult : IHttpActionResult
{
private readonly string _errorMessage;
private readonly HttpRequestMessage _requestMessage;
private readonly HttpStatusCode _statusCode;
public WebApiErrorResult(
HttpRequestMessage requestMessage,
HttpStatusCode statusCode,
string errorMessage)
{
_requestMessage = requestMessage;
_statusCode = statusCode;
_errorMessage = errorMessage;
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
return Task.FromResult(_requestMessage.CreateErrorResponse(_statusCode, _errorMessage));
}
}
WebApiConfig.cs
Finally, we register our custom exception handler with framework.
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional });
config.Services.Replace(typeof(IExceptionHandler), new WebApiExceptionHandler());
config.Filters.Add(new AuthorizeAttribute());
}
}