层叠下拉列表更新数据库调用

Question

我目前需要创建级联下拉列表

    <td>@Html.LabelFor(u => u.States)</td>
    <td>
        @Html.DropDownListFor(model => model.State, new SelectList(Model.States), new { style = "height:27px;border: 1px solid grey;", @id = "StateSelected" })                                                      
         @Html.ValidationMessageFor(u => u.States)
         @Html.HiddenFor(model => model.CustomerNumber)
    </td>                
</tr>
<tr>
    <td></td>
    <td>@Html.LabelFor(u => u.ShipToCode)</td>
    <td>
        @Html.DropDownListFor(model => model.ShipToCode, new SelectList(Model.Sites, "Code", "Address"), new { style = "height:27px;border: 1px solid grey;" })                                                      
        @Html.ValidationMessageFor(u => u.Sites)
        @Html.HiddenFor(model => model.CustomerNumber)
    </td>                
</tr>

选择第一个状态，将允许基于所选状态的更精确的地址

当前状态从控制器加载

private SitesModel GetDistinctStates(SitesModel model)
{
    model.States = new List<string>();
    using (NAVLIVEEntities entities = new NAVLIVEEntities())
    {
        try
        {
            List<GetServiceDeliveryAddress_Result> Addresses = entities.GetServiceDeliveryAddress(model.CustomerNumber).ToList();
            IEnumerable<string> Addresses_Unique = Addresses.Select(x => x.County).Distinct();
            List<string> Address_Unique_List = Addresses_Unique.ToList();
            model.States.Add("ALL STATES");
            foreach (string uniqueStates in Address_Unique_List)
            {
                model.States.Add(uniqueStates);
            }
        }
        catch (Exception ex)
        {
            ///Do nothing
        }
    }
    return model;
}

private SitesModel GetSiteAddresses(SitesModel model, string state)
{
    model.Sites = new List<SitesModel.SiteAddresses>();
    using (NAVLIVEEntities entities = new NAVLIVEEntities())
    {
        try
        {
            List<GetServiceDeliveryAddress_Result> Addresses = entities.GetServiceDeliveryAddress(model.CustomerNumber).ToList();
            foreach (var site in Addresses)
            {
                SitesModel.SiteAddresses address = new SitesModel.SiteAddresses();
                address.Code = site.Code;
                address.Address = site.Address + " " + site.Address_2 + ", " + site.City + " " + site.County + " " + site.Post_Code;
                model.Sites.Add(address);
            }
        }
    catch
    {

    }
    return model;
}

第一个控制器将列出实体的不同状态。

第二个控制器的目标是根据第一个选择的状态显示列表。

有多种实现方式，但我似乎无法用这种方式解决这个问题。

修改

在我的javascript中，正如我所说的那样

<script type="text/javascript">
    var localityUrl = '@Url.Action("FetchSites")';
    var localities = $('#FetchSites');
    $('#SelectedState').change(function () {
        var txt = $(this).val();
        alert(txt);
        $.getJSON(localityUrl, { model: @Html.Raw(Json.Encode(Model)), State: $(this).val() }, function (data) {
            if (!data) {
                return;
            }
            localities.append($('<option></option>').val('').text('Please select'));
            $.each(data, function (index, item) {
                localities.append($('<option></option>').val(item.Value).text(item.Text));
            });
        });
    })
</Script>

在控制器上执行此操作

[HttpGet]
    public JsonResult FetchSites(SitesModel model, string State)
    {
        var data = model.Sites.Where(l => l.State == State).Select(l => l.Address);

        return Json(data, JsonRequestBehavior.AllowGet);
    }

但是，我似乎没有正确传递模型，因此传递数据进行过滤。有什么建议吗？

编辑2：网站人口

private SitesModel GetSiteAddresses(SitesModel model)
    {
        model.Sites = new List<SitesModel.SiteAddresses>();
        using (NAVLIVEEntities entities = new NAVLIVEEntities())
        {
            try
            {
                List<GetServiceDeliveryAddress_Result> Addresses = entities.GetServiceDeliveryAddress(model.CustomerNumber).ToList();

                foreach (var site in Addresses)
                {
                    SitesModel.SiteAddresses address = new SitesModel.SiteAddresses();
                    address.Code = site.Code;
                    address.Address = site.Address + " " + site.Address_2 + ", " + site.City + " " + site.County + " " + site.Post_Code;
                    address.State = site.County;
                    model.Sites.Add(address);
                }
            }
            catch
            {
            }
        }
        return model;
    }