Passing parameters in ajax call

Question

I'm trying to make an ajax call to the controller method. without parameter it works fine. Once i add the parameter i always receive a null parameter to the cotroller. I think i have correctly done the parameter passing in ajax call.

 <script type="text/javascript">
        $(document).ready(function () {
            $('#lstStock').change(function () {
                var serviceURL = '<%= Url.Action("GetStockPrice", "Delivery") %>';
                var dropDownID = $('select[id="lstStock"] option:selected').val();
             alert(dropDownID); // here i get the correct selected ID
                $.ajax({
                    type: "POST",
                    url: serviceURL,
                    data: '{"stockID":"' + dropDownID + '"}',
                    contentType: "application/json; charset=utf-8",
                    dataType: "json",
                    success: successFunc,
                    error: errorFunc
                });

                function successFunc(data, status) {

                    alert(data.Result);


                }

                function errorFunc() {
                    alert('error');
                }
            })
        });
    </script>

Controller:

 [HttpGet]
        public ActionResult GetStockPrice()
        {
            return View();
        }

        [HttpPost]
        [ActionName("GetStockPrice")]
        public ActionResult GetStockPrice1(string stockID)//I get the null parameter here
        {
            DeliveryRepository rep = new DeliveryRepository();
            var value = rep.GetStockPrice(stockID);
            return Json(new { Result = value }, JsonRequestBehavior.AllowGet);

        }

Answer 1

It's because you are treating the data as a string

data: '{"stockID":"' + dropDownID + '"}',

you can change it to:

data: { stockID: dropDownID },

in some cases, depending on the parameter declared in your controller method, you need to serialize the data. If you need to do that then this is how you would do it:

var o = { argName: some_value };
$.ajax({
    // some other config goes here
    data: JSON.stringify(o),
});

Answer 2

try data: { stockID : dropDownID},

$('#lstStock').change(function () {
    var serviceURL = '<%= Url.Action("GetStockPrice", "Delivery") %>';
    var dropDownID = $('select[id="lstStock"] option:selected').val(); 
                     // $(this).val(); is better
         alert(dropDownID); // here i get the correct selected ID
            $.ajax({
                type: "POST",
                url: serviceURL,
                data: { stockID : dropDownID},
                ....