如何使用 ASP.Net MVC 级联 DropDownList

Question

我已经使用 ASP.Net MVC 实现了级联（依赖）DropDownList。但是重定向到 index.cshtml 不起作用，因为除了第一个正确填充的 DropDownList 之外，表单上的所有 DropDownList 都是空的。如何根据country dropdownlist的数据填充state dropdownlist？

控制器

public ActionResult page()
        {
            string con = Properties.Settings.Default.db;
            MySqlConnection con_main = new MySqlConnection(con);

            con_main.Open();
            MySqlCommand listK = new MySqlCommand("", con_main);
            var listcountry = new List<dropdownc>();
            listc.CommandText = "SELECT id, name FROM master_country";
            MySqlDataReader rc = listc.ExecuteReader();
            while (rc.Read())
            {
                listcountry.Add(new dropdownc
                {
                    id = rc[0].ToString(),
                    name = rc[1].ToString()
                });

            }
            ViewBag.country = new SelectList(listcountry, "id", "name");

            con_main.Close();
            return View();
        }

        [HttpPost]
        public JsonResult getstate(string Id)
        {
            string con = Properties.Settings.Default.db;
            MySqlConnection con_main = new MySqlConnection(con);
            MySqlCommand lists = new MySqlCommand("", con_main);
            var liststate = new List<dropdowns>();
            con_main.Open();
            listsc.CommandText = "SELECT id, name FROM master_state WHERE id_country = '" + Id + "' ";
            MySqlDataReader rs = listsc.ExecuteReader();
            while (rs.Read())
            {
                liststate.Add(new dropdowns
                {
                    id = rs[0].ToString(),
                    name = rs[1].ToString()
                });

            }
           
            con_main.Close();
            return Json(liststate, JsonRequestBehavior.AllowGet);
        }

查看

 <div id="dropDownListdiv">
     @using (Html.BeginForm("Index", "CascadingDropDownList", FormMethod.Post))
     {
          @Html.DropDownList("country", "Select Country")
          @Html.DropDownList("state", new SelectList(" "), "Select State")
          <input type="submit" value="Submit" />
}
</div>

JavaScript 查看代码

<script>
    $(document).ready(function () {
        $("#country").change(function () {
            $.get("~/pageControl/getstate", { Id: $("#country").val() }, function (data) {
                $("#state").empty();
                $.each(data, function (index, row) {
                    $("#state").append("<option value='" + row.id + "'>" + row.name + "</option>")
                });
            });
        })
    });
</script>

Answer 1

我会用 ajax 做这样的事情：

<script>
    $(document).ready(function () {
        $("#country").change(function () {
            BindStatesForDropDown();
        });
    });
    
    function BindStatesForDropDown() {

        var objParam = new Object();
        objParam.Id = $("#country").val();

        $.ajax({
            type: "POST",
            url: "/pageControl/getstate",
            contentType: "application/json",
            data: JSON.stringify(objParam),
            success: function (res) {
                $("#state").empty();
                if (res.length > 0) {
                    $.each(res, function (key, data) {
                        $("#state").append($("<option></option>").val(data.id).html(data.name));
                    });
                }
            },
            error: function (res) {
            }
        });
    }
</script>

如何使用 ASP.Net MVC 级联 DropDownList

How to Cascading DropDownList using ASP.Net MVC

c#

asp.net

asp.net-mvc

asp.net-mvc-4