Handling Errors with ASP.NET MVC
page 4 of 5
by Steven Smith
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Passing Error Details to an ErrorViewResult

Although usually the attribute / ActionFilter approach is the way to go, you may find that you want to have more control over how errors are handled, or you want to be able to more easily test that an Exception occurred within your controller.  In this case, you may want to create a custom ViewResult for exceptions.  Listing 4 shows an ErrorViewResult class created for this purpose.

Listing 4

    public class ErrorViewResult : ViewResult
        public Exception Exception { get; private set; }
        public ErrorViewResult(Exception exception)
            Exception = exception;
        public override void ExecuteResult(ControllerContext context)
            context.HttpContext.Response.StatusCode = 500;
            context.HttpContext.Response.TrySkipIisCustomErrors = true;
                base.ViewName = "Error";
            string controllerName = (string)context.RouteData.Values["controller"];
            string actionName = (string)context.RouteData.Values["action"];
            HandleErrorInfo info = new HandleErrorInfo(Exception, controllerName,
            ViewData.Model = info;
            if (String.IsNullOrEmpty(base.ViewName))
                base.ViewName = "ErrorDetails";


It expects an Exception in its constructor, and its ExecuteResult() method handles the rest of the work.  Note that it will respect the <customErrors /> section and if this is turned on, it will default to simply rendering the Error view.  You can remove or reconfigure this bit of logic if you'd like for this to work regardless of how customErrors are configured.  Otherwise, it simply wraps up the Exception that was passed in along with the controller and action names into a System.Web.Mvc.HandleErrorInfo object, which it then passes to a strongly typed ErrorDetails view.  Listing 5 shows this View:

Listing 5 - ErrorDetails.cshtml

<span style='background:yellow'>@model </span>System.Web.Mvc.HandleErrorInfo
<span style='background:yellow'>@{</span
    Layout = null>;
<span style='background:yellow'>}</span>
<!DOCTYPE html>
        Sorry, an error occurred while processing your request.
    <b>Error: </b>
    <p>Controller: <span style='background: yellow'>@</span>Model.ControllerName</p>
    <p>Action: <span style='background:yellow'>@</span>Model.ActionName</p>
<p><span style='background:yellow'>@</span>Model.Exception.Message</p>
<p><span style='background:yellow'>@</span>Model.Exception.ToString()</p>

Setting up a call to the ErrorViewResult would typically occur in the catch {} block, as Listing 6 shows.

Listing 6 - Returning an ErrorViewResult from an Action

        public ActionResult CreateErrorWithErrorViewResult()
                throw new ApplicationException("Something bad happened.");
            catch (Exception ex)
                return new ErrorViewResult(ex);
            return View();


The result of this action, when <customerErrors /> mode is Off, is shown here:

Naturally you can extend the functionality of the ErrorViewResult as needed, for instance if you wanted to be able to pass in the name of the View to use when rendering exceptions.

If you need to log exceptions, probably the best way to do so today is with ELMAH.  You'll find some useful code showing how to wire up ELMAH with ASP.NET MVC here.  It shows how to subclass the HandleError attribute and hook into its OnException event to control what happens when an exception occurs.

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User Comments

Title: exception   
Name: how to remove an exception
Date: 2011-03-28 6:59:43 AM
am getting an exception Function or proceedure xyz has too many arguments..

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