列表中的列表（嵌套列表）没有获取值

Question

这就是我的viewmodel的构建方式：

    public IEnumerable<EducationItem> Educations { get; set; }

    public class EducationItem
    {
        public int Id { get; set; }

        [Required]
        public string Name { get; set; }

        public FlagModel[] Flags;
     }

因此，对于每个教育项目，我都有一系列标志。

这是我的观点：

<table>
    <thead>
        <tr>
            <th>ID</th>
            <th>Education</th>
            <th>Flags</th>

        </tr>
    </thead>

    <tbody>
        @{var educations = Model.Educations.ToArray();}

        @for (int i = 0; i < educations.Length; i++)
        {
            @Html.HiddenFor(m => educations[i].Id)
            <tr>
                <td>@Html.ActionLink(educations[i].Id.ToString(), "Edit", "Education", new { id = educations[i].Id }, null)</td>
                <td>@educations[i].Name</td>
                <td>
                    <table>
                        @for (int j = 0; j < educations[i].Flags.Count(); j++)
                        {

                            var txtStartId = string.Format(@"txt_start_{0}", j);
                            var txtEndId = string.Format(@"txt_end_{0}", j);
                            var flag = educations[i].Flags.ElementAt(j);

                            <tr>

                                <td>
                                    <input type="hidden" name="educations[@i].Flags[@j].Index" value="@j" />
                                    @Html.CheckBoxFor(m => educations[i].Flags[j].Checked, new { id = string.Format("chk_flag_{0}", j) })
                                    @(Html.GetCacheModel<Flag>(flag.Id).Name)
                                </td>
                                <td>
                                    @Html.EditorFieldFor(m => educations[i].Flags[j].StartDate, "Start date", htmlAttributes: new { id = string.Format("txt_start_{0}", i) })
                                    <input type="text" name="@string.Format("Flags[{0}].StartDate",j)"/>
                                </td>
                                <td>
                                    @Html.EditorFieldFor(m => educations[i].Flags[j].EndDate, "End date", htmlAttributes: new { id = string.Format("txt_end_{0}", i) })
                                    @Html.HiddenFor(m => educations[i].Flags[j].Id)
                                </td>
                            </tr>


                        }
                    </table>
                </td>
            </tr>
        }
    </tbody>
</table>

但是当我到达我的帖子，我接受我的viewmodel作为参数时，flags为null。

我无法弄清楚为什么值不会传递。（我已尝试使用常规文本框而不是编辑器字段，但结果相同）

任何帮助将不胜感激！