How I get value by using selected dropdown list value as parameter and get value from data-table

$(document).ready(function () {
        $("#ProdID").change(function () {
            var pID = ($("#ProdID").val());
            var url = "/Perchus/GetTaxRt";
            $.post(url, { ProductId: pID }, function (data) {
                $.each(data, function (Row) {
                    $("#PGstRate").append("<option value='" + row.ProducID + "'>" + row.Gst_taxRate + "</option>")
                });

                alert("You May Edit This Tax Rat IF You May It ...")
            });

        });
    });

[HttpPost]
       public JsonResult GetTaxRt(PerchesDetail pd, int ProductId)
       {
           var ttx = dc.Product_master.Where(p => p.ProducID == ProductId).FirstOrDefault();
           pd.PGstRate = ttx.Gst_taxRate;
           return Json(pd.PGstRate, JsonRequestBehavior.AllowGet);
       }