jquery - DropDownList 在回发或验证失败时没有要选择的项目

Question

我的视图“州”和“区”上有两个 DropDownList。我使用以下代码填充“状态”DDL。

控制器：-

var districts = (from r in db.Districts
                     select new { r.DistrictName });
ViewBag.DistrictName = new SelectList(districts, "DistrictName", "DistrictName");

看法：-

@Html.DropDownList("State", ViewBag.StateName as SelectList, "Select a State")

现在，每当一个人选择州时，JSON致电填充了“地区的DDL。

控制器：-

[HttpGet]
public JsonResult DistrictList(string Id)
{
    var districts = (from d in db.Districts
                        where d.State.StateName == Id
                        select new { d.DistrictName });
    return Json(new SelectList(districts, "DistrictName", "DistrictName"), JsonRequestBehavior.AllowGet);
}

看法：-

<select id="District"  name="District"></select>
<script type="text/jscript">
    $(function () {
        $('#State').change(function () {
            $.getJSON('/Application/DistrictList/' + $('#State').val(), function (data) {
                var items = '<option>Select a District</option>';
                $.each(data, function (i, districts) {
                    items += "<option value='" + districts.Text + "'>" + districts.Text + "</option>";
                });
                $('#District').html(items);
            });
        });
    });
</script>

它工作正常，但问题是，每当任何验证失败时，'District' DDL 都会丢失其数据。我再次需要在“州”中进行新的选择，然后“区”从 Json resutl 中获取数据。如何处理？

Answer 1

给你的第一个选项一个虚拟值，然后在后端检查它：

var items = '<option value="-1">Select a District</option>';