Exception handling in ASP.NET MVC

ASP.NET MVC 4

By default in asp.net MVC the exceptions are handled by the controller if you enable the customErrors in web.config. The error.cshtml in shared folder is called when ever there is an exception in actionMethod.

<system.web>
    <customErrors mode="On">
    </customErrors>
</system.web>

However if you need custom errors of you choice, then you need to use the HandleError attribute.

 [HandleError( View = "PageNotFound")]

In the below snippet, the result due to 1/0, raises the arthimetic exception then calls the ArthimeticExeView by the HandleError attribute

Code Snippet:

HomeController:

[HandleError(ExceptionType = typeof(ArithmeticException), View = "ArthimeticExeView")]

        public ActionResult TestHandleError()

        {

            var a = 1;

            var b = 0;

            var result = a / b;

            return View();

        }


ArthimeticExeView.cshtml:

<h1>Attempted to divide by zero.</h1>

The above method has a drawback of re-usability. Because it has a view name(ArthimeticExeView) that contains the message for arithmetic exception In order to keep a common view for all exceptions, then we need to pass the exception message using the custom error handling attribute. 

In CustomErrHandler we override the onException method and returns the exception message to view model.

Code Snippet:

HomeController:

             [CustomErrHandler]

        public ActionResult TestHandleError2()

        {

            var a = 1;

            var b = 0;

            var result = a / b;

            return View();

        }

CustomErrHandler.cs:

    public class CustomErrHandler : HandleErrorAttribute

    {

        public override void OnException(ExceptionContext filterContext)

        {

            Exception ex = filterContext.Exception;

            filterContext.ExceptionHandled = true;

            var model = new HandleErrorInfo(filterContext.Exception, "Controller", "Action");

            filterContext.Result = new ViewResult()

            {

                ViewName = "Error1",

                ViewData = new ViewDataDictionary(model)

            };

        }

    }

Error1.cshtml:

@model System.Web.Mvc.HandleErrorInfo

@{

    ViewBag.Title = "Error";

}

<h1>@ViewData.Model.Exception.Message</h1>