Question

我正在尝试创建一个由一系列下拉列表组成的表单，所有下拉列表都是从数据库加载的。我不知道需要多少下拉列表，或者每个下拉列表在编译时有多少选项。

如何设置这些字段以允许它们在发布时进行模型绑定？

下面的每个代码元素都有很多其他复杂性，但即使降低到基本级别，我也无法使模型绑定工作。

模特：

public class MyPageViewModel
{
    public List<MyDropDownListModel> ListOfDropDownLists { get; set; }
}

public class MyDropDownListModel
{
    public string Key { get; set; }
    public string Value { get; set; }
    public List<SelectListItem> Options { get; set; }
}

Controller Get Action：

[AcceptVerbs(HttpVerbs.Get)]
[ActionName("MyAction")]
public ActionResult MyGetAction()
{
    var values_1 = new List<string> {"Val1", "Val2", "Val3"};
    var options_1 =
        values_1
            .ConvertAll(x => new SelectListItem{Text=x,Value=x});

    var myDropDownListModel_1 =
        new MyDropDownListModel { Key = "Key_1", Options = options_1 };


    var values_2 = new List<string> {"Val4", "Val5", "Val6"};
    var options_2 =
        values_2
            .ConvertAll(x => new SelectListItem{Text=x,Value=x})};

    var myDropDownListModel_2 =
        new MyDropDownListModel { Key = "Key_2", Options = options_2 };


    var model =
        new MyPageViewModel
        {
            ListOfDropDownLists = 
                new List<MyDropDownListModel>
                {
                    myDropDownListModel_1,
                    myDropDownListModel_2,
                }
        };

    return View(model);
}

Controller Post Action：

[AcceptVerbs(HttpVerbs.Post)]
[ActionName("MyAction")]
public ActionResult MyPostAction(MyPageViewModel model)
{
    //Do something with posted model...
    //Except 'model.ListOfDropDownLists' is always null

    return View(model);
}

观点：

@model MyPageViewModel

@using (Html.BeginForm("MyPostAction"))
{
    foreach (var ddl in Model.ListOfDropDownLists)
    {
        @Html.DropDownListFor(x => ddl.Value, ddl.Options)
    }
    <button type="submit">Submit</button>
}

修改：纠正错别字和复制粘贴错误。

解决方案：

问题原来是视图中的foreach循环。将其更改为for循环会导致帖子按预期填充。更新后的视图如下：

@using (Html.BeginForm("MyPostAction"))
{
    for (int i = 0; i < Model.ListOfDropDownLists.Count; i++)
{
        @Html.HiddenFor(x => x.ListOfDropDownLists[i].Key)
        @Html.DropDownListFor(m => m.ListOfDropDownLists[i].Value, Model.ListOfDropDownLists[i].Options);
    }
    <button type="submit">Submit</button>
}

Answer 1

您的视图仅创建多个名为dll.Value的选择元素（和重复的ID），这些元素与您的模型无关。您需要的是创建名为ListOfDropDownLists[0].Value, ListOfDropDownLists[1].Value等的元素。

将视图中的循环更改为此

for (int i = 0; i < Model.ListOfDropDownLists.Count; i++)
{     
    @Html.DropDownListFor(m => m.ListOfDropDownLists[i].Value, Model.ListOfDropDownLists[i].Options);
}

您发布的代码有多处错误（例如，您传递了MyPageViewModel类型的模型，但后期操作方法需要MyModel类型。我认为这些只是错字。

Answer 2

我可以给你解决方案，它正在发挥作用：

基本控制器中的方法

//To bind Dropdown list 
    protected Dictionary<int, string> GenerateDictionaryForDropDown(DataTable dtSource, string keyColumnName, string valueColumnName)
    {
        return dtSource.AsEnumerable()
          .ToDictionary<DataRow, int, string>(row => row.Field<int>(keyColumnName),
                                    row => row.Field<string>(valueColumnName));
    }

控制器中的代码：

    DataTable dtList = new DataTable();

    dtList = location.GetDistrict();
    Dictionary<int, string> DistrictDictionary = GenerateDictionaryForDropDown(dtList, "Id", "DistrictName");
    model.DistrictList = DistrictDictionary;

在视图中绑定数据：

 @Html.DropDownListFor(model => model.DiscrictId, new SelectList(Model.DistrictList, "Key", "Value"), new { id = "ddlDist", @class = "form-control" })

绑定其他下拉列表（级联）：其他下拉：

@Html.DropDownListFor(model => model.TalukaId, new SelectList(Model.TalukaList, "Key", "Value"), new { id = "ddlTaluka", @class = "form-control" })

JQuery代码： $（“＃ddlDist”）。change（function（）{ var TalukaList =“选择” $（ '＃ddlTaluka'）HTML（TalukaList）;

        $.ajax({
            type: "Post",
            dataType: 'json',
            url: 'GetTaluka',
            data: { "DistId": $('#ddlDist').val() },
            async: false,
            success: function (data) {
                $.each(data, function (index, optionData) {
                    TalukaList = TalukaList + "<option value='" + optionData.Key + "'>" + optionData.Value + "</option>";
                });
            },
            error: function (xhr, status, error) {
                //alert(error);
            }
        });
        $('#ddlTaluka').html(TalukaList);
    });

控制器方法返回JSON

public JsonResult GetTaluka(int DistId)
{
    LocationDH location = new LocationDH();
    DataTable dtTaluka = location.GetTaluka(DistId);
    Dictionary<int, string> DictionaryTaluka = GenerateDictionaryForDropDown(dtTaluka, "ID", "TalukaName");
    return Json(DictionaryTaluka.ToList(), JsonRequestBehavior.AllowGet);
}

我如何模型绑定列表<selectitem>＆＃39;使用MVC.Net </selectitem>

2 个答案: