Catch me catch me if you can - Errors on MVC

There are so many articles about the various ways to handle errors that you probably don't need another one. I am just going to focus on some key points and some gotchas!

The 404 Error
(Page or Route not found -
                    is not as much an error as an exception and it is handled differently)

This is why we typically reference a special page for 404 errors in our config

    <customErrors mode="On" defaultRedirect="error" >
             <error statusCode="404" redirect="~/error/error_notfound"/>
    </customErrors>

Make sure in your App_Start FilterConfig file that you are adding the filter for HandleErrorAttribute

   filters.Add(new HandleErrorAttribute());

I have implemented a custom Error handler  as well so I have a filter included for that file

      filters.Add(new CustomErrorHandling());


    public class CustomErrorHandling : HandleErrorAttribute,  IExceptionFilter
{
    public override void OnException(ExceptionContext filterContext)
        {
            if (filterContext.ExceptionHandled || !filterContext.HttpContext.IsCustomErrorEnabled)
            {
                return;
            }
       

            if (new HttpException(null, filterContext.Exception).GetHttpCode() != 500)
            {
                return;
            }

            if (!ExceptionType.IsInstanceOfType(filterContext.Exception))
            {
                return;
            }

            // if the request is AJAX return JSON else view.
            if (filterContext.HttpContext.Request.Headers["X-Requested-With"] == "XMLHttpRequest")
            {
                filterContext.Result = new JsonResult
                {
                    JsonRequestBehavior = JsonRequestBehavior.AllowGet,
                    Data = new
                    {
                        error = true,
                        message = filterContext.Exception.Message
                    }
                };
            }
            else
            {
                var controllerName = (string)filterContext.RouteData.Values["controller"];
                var actionName = (string)filterContext.RouteData.Values["action"];
                var model = new HandleErrorInfo(filterContext.Exception, controllerName, actionName);
           
                filterContext.Result = new ViewResult
                {
                    ViewName = View,
                    MasterName = Master,
                    ViewData = new ViewDataDictionary(model),
                    TempData = filterContext.Controller.TempData
                };
              //  ExceptionUtility.NotifyWebTeam(filterContext.Exception);
            }

My default redirect goes to "error" - So rather than depend on the Home Controller  I added an Error Controller and am landing on the default page with some generic code  as shown:

   <h3 class="text-danger">Error.</h3>
            <h4 class="text-danger">An error occurred while processing your request.</h4>
            Controller: @Model.ControllerName<br />
            Action:@Model.ActionName.ToString()<br /><br />
            @if (Model.Exception.InnerException != null)
            {
                @Model.Exception.InnerException.StackTrace;
                @Request.IsLocal;
                @Model.Exception.InnerException.Message;
            }


            Message: @Model.Exception.Message<br />

            @if (Model.Exception.Message != null && Model.Exception.Message.ToString().Contains("A potentially dangerous Request.Form"))
            {
                @:Our system does not accomodate HTML.  Please use the browsers back button to review your entries and try again.

            }
            else
            {

                @:Our web team has been notified of this issue.
      }




        }
    }
}