gistfile1.cs

    public class Attribute : ActionFilterAttribute {
        public override void OnActionExecuted(ActionExecutedContext filterContext) {
            base.OnActionExecuted(filterContext);

            if (!filterContext.ExceptionHandled) {
                var exception = filterContext.Exception;

                if (exception is CustomException) {
                    filterContext.Controller.ViewData.ModelState.Add(String.Empty, Resource.CustomExceptionMessage);
                }
                else if (excetion is Exception) {
                    filterContext.Controller.ViewData.ModelState.Add(String.Empty, Resource.GenericExceptionMessage);
                }
            }
        }
    }