C# ajax读取后台接口，填充给select下拉框

C#，后台接口（post方式）来获取所有板块的名字，路由如下所示：
[HttpPost]
[Route("shuliang/getallName")]

接口返回如下json：
{
“BankuaiNames”：
[
"板块1"
"板块2"
"板块3"
"板块4"
]
}

现在想要在前台通过ajax，读取后台接口返回的json，并且用js绑定到select下拉框，
进行显示
如下图所示

求指点

 using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

namespace Q694264.Controllers
{
    [HandleError]
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            ViewData["Message"] = "Welcome to ASP.NET MVC!";

            return View();
        }

        public ActionResult About()
        {
            return View();
        }

        [HttpPost]
        public string getallName()
        { 
            return @"{
    ""BankuaiNames"":
    [
        ""板块1"",
        ""板块2"",
        ""板块3"",
        ""板块4"",
        ""asdf""
    ]
}";
        }
    }
}

 <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    Home Page
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">
    <h2><%: ViewData["Message"] %></h2>
<%--    <p>
        To learn more about ASP.NET MVC visit <a href="http://asp.net/mvc" title="ASP.NET MVC Website">http://asp.net/mvc</a>.
    </p>--%>
    <script type="text/javascript">
        window.onload = function () {
            $.ajax({
                url: "/home/getallName",
                type: "POST",
                data: "",
                dataType: "json",
                success: function (data) {
                    for (var i = 0; i < data.BankuaiNames.length; i++) {
                        $("#yys").append("<option>" + data.BankuaiNames[i] + "</option>");
                    }
                },
                error: function (data) {
                    alert("err");
                }
            });
        };
    </script>
    运营商：<select id="yys" name="yys">
        <option>--请选择运营商---</option>
    </select>
</asp:Content>

完整代码下载：https://download.csdn.net/download/caozhy/10531288 （因为审核的原因，请明天上午9点以后再访问）

如果问题解决，请及时采纳，谢谢。