ASP.NET MVC - Declarative Redirect On Error

Question

I have been capturing exceptions and redirecting users to an error page. I pass the exception message and a return URL to tell the user what happened and allow them to return another page.

        try
        {
            return action(parameters);
        }
        catch (Exception exception)
        {
            ErrorViewModel errorModel = new ErrorViewModel();
            errorModel.ErrorMessage = "An error occured while doing something.";
            errorModel.ErrorDetails = exception.Message;
            errorModel.ReturnUrl = Url.Action("Controller", "Action");
            return RedirectToAction("Index", "Error", errorModel);
        }

This seems like way too much code to wrap around every action. I am using a global filter for errors:

    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        HandleErrorAttribute attribute = new HandleErrorAttribute();
        filters.Add(attribute);
    }

and I have my web.config setup like this:

<customErrors mode="On" defaultRedirect="~/Error/Unknown">

But, this only works for unhandled exceptions.

I want exceptions to cause a redirect to an error controller/action taking a parameter holding the exception details. It would be nice if I could indicate the return URL on a action-by-action basis, or to have a default if none is provided.

Answer 1

Here is a little RedirectOnErrorAttribute class I created:

using System;
using System.Web.Mvc;
using MyApp.Web.Models;

namespace MyApp.Web.Utilities
{
    public class RedirectOnErrorAttribute : ActionFilterAttribute
    {
        /// <summary>
        /// Initializes a new instance of a RedirectOnErrorAttribute.
        /// </summary>
        public RedirectOnErrorAttribute()
        {
            ErrorMessage = "An error occurred while processing your request.";
        }

        /// <summary>
        /// Gets or sets the controller to redirect to.
        /// </summary>
        public string ReturnController { get; set; }

        /// <summary>
        /// Gets or sets the action to redirect to.
        /// </summary>
        public string ReturnAction { get; set; }

        /// <summary>
        /// Gets or sets the error message.
        /// </summary>
        public string ErrorMessage { get; set; }

        /// <summary>
        /// Redirects the user to an error screen if an exception is thrown.
        /// </summary>
        /// <param name="filterContext">The filter context.</param>
        public override void OnActionExecuted(ActionExecutedContext filterContext)
        {
            if (filterContext.Exception != null && !filterContext.ExceptionHandled)
            {
                ErrorViewModel viewModel = new ErrorViewModel();
                viewModel.ErrorMessage = ErrorMessage;
                viewModel.ErrorDetails = filterContext.Exception.Message;
                string controller = ReturnController;
                string action = ReturnAction;
                if (String.IsNullOrWhiteSpace(controller))
                {
                    controller = (string)filterContext.RequestContext.RouteData.Values["controller"];
                }
                if (String.IsNullOrWhiteSpace(action))
                {
                    action = "Index";
                }
                UrlHelper helper = new UrlHelper(filterContext.RequestContext);
                viewModel.ReturnUrl = helper.Action(action, controller);
                string url = helper.Action("Index", "Error", viewModel);
                filterContext.Result = new RedirectResult(url);
                filterContext.ExceptionHandled = true;
            }
            base.OnActionExecuted(filterContext);
        }
    }
}

Now, I can decorate all of my actions like this:

[RedirectOnError(ErrorMessage="An error occurred while doing something.", ReturnController="Controller", ReturnAction="Action")]

Answer 2

Instead of putting a try catch in every action, you could override the OnException event of the controller. That event contains all the exception details. All of you other settings look right.

    [HandleError]
    public class AccountController : Controller
    {
       [HttpPost]
       public ActionResult YourAction(SomeModel model)
        {
            //do stuff but don't catch exception
            return View();
        }
        protected override void OnException(ExceptionContext filterContext)
        {
            EventLog.WriteEntry("YourProjectEventName", filterContext.Exception.ToString(), EventLogEntryType.Error);
            base.OnException(filterContext);
       }
}