.ajax函数结果似乎未从控制器返回

如何解决.ajax函数结果似乎未从控制器返回

我有一个Ajax函数，它会在我的下拉列表更改时触发：

<select id="SCat_Cat" name="SCat_Cat" asp-for="Cat_Id" asp-items="(SelectList)ViewBag.Cat_ID" class="form-control" onchange="funct()">
      <option value="0">Select Category</option>
</select>

应对此进行更新：

<select id="SCat_SCat" name="SCat_SCat" asp-for="SCat_ID" asp-items="(SelectList)ViewBag.Scat_ID" class="form-control">
       <option value="0">Select SubCategory</option>
</select>

.ajax代码：

<script type="text/javascript">
    function funct() {
        var catvalue = document.getElementById("SCat_Cat").value;
        var url = "CreatePopulateScat"
        alert(catvalue);
        $.ajax(
            {
                type: "POST",url: url,data: { CatID: catvalue },success: function (result) {
                    if (result.success) {
                        alert("Good");
                        document.getElementById("SCat_SCat").innerHTML = result;                     
                    }
                },error: function (req,status,error) {
                    alert("Error");
                }
            });
        return false;
    }
</script>

以及控制器代码：

        public async Task<IActionResult> Create()
        {
            ViewBag.Cat_ID = new SelectList(_context.Category,"Cat_ID","Cat_Name");
            var specialists = await userManager.GetUsersInRoleAsync("Specialist");
            ViewBag.Specialist_ID = new SelectList(specialists,"Id","UserName");
            return Request.IsAjaxRequest() ? (IActionResult)PartialView() : View();
        }

        [HttpPost]
        public IActionResult CreatePopulateSCat(string CatID)
        {
            List<SubCategory> AllSubCategories = _context.SubCategory.ToList();
            List<SubCategory> SelectedSubCategories = AllSubCategories.FindAll(a => a.SCat_Cat.Contains(CatID));
            ViewBag.SCat_ID = new SelectList(SelectedSubCategories,"SCat_ID","SCat_Name");
            return Request.IsAjaxRequest() ? (IActionResult)PartialView("Create") : View("");
        }

使用断点，我可以知道ajax脚本向控制器发送了正确的数据，并且收集了列表，但是它不返回任何内容，甚至没有经过success代码显示alert("Good");或alert("Error");