How do I return json with error message

Question

Hi all I'm using ajax to call detail model by Id. But I want to display a message if model return data is null. How do I ?

my code ajax to display details model

$('#PGId').blur(function () {
        var errormsg = "";
        var id = $('#PGId').val();
        $.ajax({
            type: "GET",
            url: '@Url.Action("GetDetailPG", "TimeSheetHeader")',
            data: { pgId: id },
            dataType: "json",
            success: function (data) {
               success: function (data) {
                if (data.isValid) {
                    $("#FullName").text(data.FisrtName + " " + data.LastName)
                    $('.Shiff[value="' + data.ShiffId + '"]').prop('checked', true)
                }
                else {
                    alert(data.error);
                }
            },
            },
            error: function () {

            }
        });
    })

my controller to bind data

[HttpGet]
    public ActionResult GetDetailPG(string pgId)
    {
        PGProfileViewModel pgProfileModel = new PGProfileViewModel();
        pgProfileModel.PGId = pgId;
        var query = _pgProfileService.GetPGProfileById(pgProfileModel.PGId);
        var model = query.ToViewModel();

        if (model == null)
        {
            return Json(new {isValid = false, error = "Error Message"}, JsonRequestBehavior.AllowGet);
        }
        else
        {
            model.LastName = query.LastName.Trim();
            model.FisrtName = query.FisrtName.Trim();
            model.ShiffId = query.ShiffId;
            return Json(new { model = model , isValid = true }, JsonRequestBehavior.AllowGet);
        }
    }

Solution

If you returns a json object (as business model error) the javascript data value (which has the request result) will never be null.

You can try an approach like this:

C#

[HttpGet]
public ActionResult GetDetailPG(string pgId)
{
  PGProfileViewModel pgProfileModel = new PGProfileViewModel();
  pgProfileModel.PGId = pgId;
  var query = _pgProfileService.GetPGProfileById(pgProfileModel.PGId);
  var model = query.ToViewModel();

  if (model == null)
  {
    return Json({
      isValid: false,
      error: "Your error message"
    }, JsonRequestBehavior.AllowGet);
  }
  else
  {
    model.LastName = query.LastName.Trim();
    model.FisrtName = query.FisrtName.Trim();
    model.ShiffId = query.ShiffId;

    return Json({
      model: model,
      isValid: true
      }, JsonRequestBehavior.AllowGet);
   }
}

JS

//success function of your ajax request.
success: function (data) {
  if (data.isValid) {
    $("#FullName").text(data.FisrtName + " " + data.LastName)
    $('.Shiff[value="' + data.ShiffId + '"]').prop('checked', true)
  }
  else {
    alert(data.error);
  }
}

Comments

[wigs]

based on the original users comment to his own post he wants to send the error message from the controller. You should update the code to include an additional error message property in the json object that can be used in the js else statement.