如何在下拉列表

Question

我需要创建一个Trail，这条路径有子路径，子路径有水平，我有三个DropDownList。其中trail有一个下拉列表和相同的子轨道和级别。

问题是当我尝试创建新的Trail时，因为下拉列表中有一个TrailId来显示所有已存在的路径，具体取决于选择了哪条路径，运行ajax以过滤子路径并显示单个子路径，具体取决于所选路径

此视图是在创建时：

View Creating 这段代码是视图：

@model DefinityFirst.Mobile.Admin.Web.Services.Marvel.Contracts.ListTrailSubTrailLevelContract
@inject DefinityFirst.Mobile.Admin.Web.Services.Marvel.IMarvelServices DropDownDataHelper

@{
    ViewBag.Title = "Create";
}@if (!ViewData.ModelState.IsValid)
{
    <div class="alert alert-danger alert-dismissible" role="alert">
        <button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">&times;</span></button>
        <strong>Warning!</strong> @Html.ValidationMessage("Error")
    </div>
}
<h2>Create</h2>
<p>New TrailSubTRailLEvel</p>
@using (Html.BeginForm("TrailSubTrailLevel", "TrailSubTrailLevel", FormMethod.Post, new { id = "demoForm" }))
{
    @Html.AntiForgeryToken()
    <div class="form-horizontal">
        <h4>Trail</h4>

        <div class="form-group" id="divOne">
            @Html.Label("", "Trail", new { @class = "control-label col-md-2" })
            <div class="col-md-10" id="partialDiv">

                @Html.DropDownListFor(model => model.TrailId, await DropDownDataHelper.GetTrailsDdl(), "Select one", new { @class = "form-control", onchange = "SelectedIndexChanged()" })

                @Html.ValidationMessageFor(model => model.TrailId, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.Label("", "SubTrail", new { @class = "control-label col-md-2", @name = "Subtrail", @id = "Subtrail" })
            <div class="col-md-10">

                @Html.DropDownList("SubTrailId", new SelectList(string.Empty, "Value", "Text"), "Please select a SubTrail", new { @class = "form-control", @id = "SubtrailId", @name = "SubtrailId" })
                @Html.ValidationMessageFor(model => model.SubtrailId, "", new { @class = "text-danger" })
            </div>
        </div>

        <div class="form-group">
            @Html.Label("", "Level", new { @class = "control-label col-md-2", @name = "Level", @id = "Level" })
            <div class="col-md-10">

                @Html.DropDownListFor(model => model.LevelId, await DropDownDataHelper.LevelsDdl(), "Select one", new { @class = "form-control" })
                @Html.ValidationMessageFor(model => model.LevelId, "", new { @class = "text-danger" })
            </div>
        </div>




        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="Create" class="btn btn-success" />
            </div>
        </div>

    </div>
}
<div>
    @Html.ActionLink("Back to List", "Index")
</div>

@section Scripts {
    <script type="text/javascript">

        $('#SubtrailId').hide();
        $('#LevelId').hide();
        $("#Subtrail").hide();
        $("#Level").hide();

        $('#TrailId').on('change', function () {

            if (this.value != 0) {
                $("#Subtrail").show();
                $('#SubtrailId').show();



            } else {
                $('#SubtrailId').hide();
                $('#LevelId').hide(); 
            }
        })
        $('#SubtrailId').on('change', function () {

            if (this.value != 0) {

                $("#Level").show();
                $('#LevelId').show();


            } else {

                $('#LevelId').hide();

            }
        })

    </script>

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <script type="text/javascript">
        var URL = 'http://localhost:51514/api/TrailSubTrailLevel/JSonSubTrails';
        var dllDropDownSubTrail = $('#SubtrailId');
        var dllDropDownTrail = $('#TrailId').val();

        $(document).ready(function () {
            $('#TrailId').change(function () {
                $('#SubtrailId').html("");
                var val = $(this).val();
                $.ajax({
                    type: 'GET',
                    url: URL,
                    contentType: "application/json; charset=utf-8",
                    dataType: 'json',
                    success: function (data) {
                        var myData = data.Value;
                        localStorage.setItem('myList', myData);

                        $.each(myData, function (key, value) {
                            if (value.TrailId == $('#TrailId').val()) {
                                console.log(value.Name)
                                $('#SubtrailId').append('<option value="' + value.Id + '">' + value.Name + '</option>');
                            }
                        });
                    },

                    error: function (data) {
                        console.log('ERROR', data.Value);
                    }
                });

            });
        });
    </script>



}

这段代码是点击按钮创建的接收动作，发送所有DropDownList的信息：

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create(ListTrailSubTrailLevelContract ListTrailSubTrailLevelContract)
{


    if (ModelState.IsValid)
    {
        await _marvelServices.CreateTrailSubTrailLevel(ListTrailSubTrailLevelContract);

        return RedirectToAction("Index", "TrailSubTrailLevel");
    }


    return View(ListTrailSubTrailLevelContract);
}

而且这个代码是发送属性的地方，但我需要单独使用这个属性“TrailSubTrailId”，因为在我的表中只存在两个属性“LevelId”和“TrailSubtrailId”，但是我发送了三个属性，这就是启动问题：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace DefinityFirst.Mobile.Admin.Web.Services.Marvel.Contracts
{
    public class ListTrailSubTrailLevelContract
    {

        public int id { get; set; }

        public int TrailId { get; set; }

        public string TrailName { get; set; }

        public int SubtrailId { get; set; }

        public string SubTrailName { get; set; }

        public int LevelId { get; set; }

        public string LevelName { get; set; }

        public int TrailSubtrailId { get; set;  }

    }
}

此部分是消费服务

此代码为TrailSubTrailContract：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DefinityFirst.CarrerPath.Model.Contracts
{
    public class TrailSubTrailLevelContract
    {
        public TrailSubTrailLevelContract()
        {
            //Level = new HashSet<LevelContract>();
            //TrailSubtrail = new HashSet<TrailsSubTrailsListContract>();
        }

        public int Id { get; set; }

        public int TrailSubtrailId { get; set; }

        public int LevelId { get; set; }

        public TrailsSubTrailsListContract TrailSubtrail { get; set; }

        public LevelContract Level { get; set; }
    }
}