Question

I am returning the following object JsonResult

return new JsonResult
            {
                Data = new { ErrorMessage = message },
                ContentEncoding = System.Text.Encoding.UTF8,
                JsonRequestBehavior = JsonRequestBehavior.DenyGet
            };

How do I get the error message out of it on the jquery side?

this is my error delegate of jquery ajax

error: function (result) {
        alert('error');
        alert(result.ErrorMessage);
    }

But it alerts as undefined. I tried result.Data as well as result.message….all undefined.

namespace myApp.ActionFilters
{
    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
    public class AjaxException : ActionFilterAttribute, IExceptionFilter
    {
        public void OnException(ExceptionContext filterContext)
        {
            if (!filterContext.HttpContext.Request.IsAjaxRequest()) return;

            filterContext.Result = AjaxError(filterContext.Exception.Message, filterContext);

            //Let the system know that the exception has been handled
            filterContext.ExceptionHandled = true;
        }

        protected JsonResult AjaxError(string message, ExceptionContext filterContext)
        {
            //If message is null or empty, then fill with generic message
            if (String.IsNullOrEmpty(message))
                message = "Something went wrong while processing your request. Please refresh the page and try again.";

            //Set the response status code to 500
            filterContext.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError;

            //Needed for IIS7.0
            filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;

            return new JsonResult
            {
                Data = new { ErrorMessage = message },
                ContentEncoding = System.Text.Encoding.UTF8,
                JsonRequestBehavior = JsonRequestBehavior.DenyGet
            };
        }
    }
}

In my Controller I have an Action to test this

 [AjaxException]
    public ActionResult TestErrorHandling(string id)
    {
       if (string.IsNullOrEmpty(id))
        {
            throw new Exception("oh no");
        }
        return Json(new { success = true });
     }

In my js

 id = "";
 $.ajax({
    contentType: 'application/json, charset=utf-8',
    type: "POST",
    url: "/Controller/TestErrorHandling",
    data: JSON.stringify({ id: id }),
    cache: false,
    dataType: "json",

    success: function (result) {
        alert('some error occurred: ' + result.ErrorMessage);


        alert('success!');
    },

    error: function (xhr, ajaxOptions, thrownError) {
        alert('error');
        alert(xhr.ErrorMessage);
    }

    });

Question: how do I get the errorMessage inside error delegate?

Answer 1

How do I get the error message out of it on the jquery side?

Since you are returning a JSON object that comes with 200 status code the error callback will never be executed. So you could use the success callback in this case:

success: function(result) {
    if (result.ErrorMessage) {
        alert('some error occurred: ' + result.ErrorMessage);
    }
}

Or if you want the error handler to be executed make sure that you set the proper status code in your controller action:

public ActionResult Foo()
{
    Response.StatusCode = 500;
    return Json(new { ErrorMessage = message });
}

and then:

error: function (jqXHR) {
    var result = $.parseJSON(jqXHR.responseText);
    alert('some error occurred: ' + result.ErrorMessage);
}

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