请教个JSON异步获取的问题
后台代码

[HttpPost]
        public JsonResult GetShipId()
        {
            var ship = db.chartered_ship_base_info.ToList();
            StringBuilder sb = new StringBuilder();
            sb.Append("<option value=\"-1\">select....</option>");
            foreach (var item in ship)
            {
                sb.AppendFormat("<option value=\"{0}\">{1}</option>", item.chartered_ship_number, item.chartered_ship_number);
            }
            string result = sb.ToString();
            return this.Json(result, JsonRequestBehavior.AllowGet);
        }

        [HttpPost]
        public JsonResult GetCabinId(string shipnumber)
        {
            
            var cabin = db.ship_cabin_info.Where(c => c.chartered_ship_number == shipnumber).ToList();
            StringBuilder sb = new StringBuilder();
            sb.Append("<option value=\"-1\">select.....</option>");
            foreach (var item in cabin)
            {
                sb.AppendFormat("<option value=\"{0}\">{1}</option>", item.cabin_number, item.cabin_number);
            }
            string result = sb.ToString();
            return this.Json(result, JsonRequestBehavior.AllowGet);
        }




前台代码
<script type="text/javascript">

    $(function () {
        $.ajax({
            url: "/TestJosn/GetShipId",
            type: "POST",
            contentType: "application/json; charset=utf-8",
            data: "{}",
            dataType: "json",
            success: function (data)