回发后嵌套的ViewModel Collections为null

Question

我有以下ViewModels;

public class InformationSystemsViewModel
{
    public List<RoleViewModel> Roles { get; set; }      
}    

public class RoleViewModel
{
    public string Name { get; set; }
    public Guid HireRequestId { get; set; }
    public string RoleId { get; set; }
    public List<CompanyViewModel> Companies { get; set; }      
}

public class CompanyViewModel
{
    public int CompanyId { get; set; }
    public bool IsSelected { get; set; }
    public string Name { get; set; }        
}

以下代码在我的控制器中;

public ActionResult InformationSystems(Guid Id)
        {
            var nhr = oimRepo.GetHireRequest(Id);
            var vm = AutoMapper.Mapper.Map<HireRequest, InformationSystemsViewModel>(nhr);

            IEnumerable<Company> companies = ListCompanies();
            IEnumerable<Role> roles = ListRoles();

            List<RoleViewModel> listOfRoles = roles.Select(x => new RoleViewModel()
            {
                Name = x.Role,
                HireRequestId = Id,
                RoleId = x.RoleId,
                Companies = companies.Select(y => new CompanyViewModel()
                {
                    CompanyId = y.CompanyId,
                    Name = y.Company,
                    IsSelected = (vm.Roles == null ? false : vm.Roles.Any(a => a.HireRequestId == Id && a.RoleId == x.RoleId))
                }).ToList()
            }).ToList();

            vm.Roles = listOfRoles;

            return View(vm);
        }

       [HttpPost]
        public ActionResult InformationSystems(InformationSystemsViewModel Model)
        {

            if (ModelState.IsValid)
            {
                HireRequest nhr = oimRepo.GetHireRequest(Model.Id);
                AutoMapper.Mapper.Map<InformationSystemsViewModel, HireRequest>(Model, nhr);

                oimRepo.Save(CurrentUser.Id);

                var roles = Model.Roles;
                    var rList = new List<RoleViewModel>();
                    var cList = new List<CompanyViewModel>();

                    foreach(var r in roles)
                    {
                        var companies = r.Companies;
                        if(companies != null)
                        {
                            foreach(var c in companies)
                            {
                                var cvm = new CompanyViewModel()
                                {
                                    CompanyId = c.CompanyId,
                                    IsSelected = c.IsSelected,
                                    Name = c.Name
                                };

                                cList.Add(cvm);
                            }

                            var rvm = new RoleViewModel()
                            {
                                Companies = cList,
                                HireRequestId = r.HireRequestId,
                                Name = r.Name,
                                RoleId = r.RoleId
                            };

                            rList.Add(rvm);
                        }
                    }

                    var gpAccess = AutoMapper.Mapper.Map<IEnumerable<RoleViewModel>, List<HireRequest_Access>>(rList);
                    oimRepo.CreateGPAccess(gpAccess);
                    oimRepo.Save(CurrentUser.Id);
                }

                return RedirectToAction("Review", new { id = Model.Id });
            }

            return View(Model);
        }

最后我的Razor标记;

<table id="Roles" data-height="600" data-toggle="table" data-show-columns="false" data-striped="true" data-fixed-columns="false" data-fixed-number="1">
                        <thead>
                            <tr>
                                <th>Role</th>
                                @foreach (var company in Model.Roles.FirstOrDefault().Companies)
                                {
                                    <th data-id="@company.CompanyId" data-field="@company.Name">@company.Name</th>
                                }
                            </tr>
                        </thead>
                        <tbody>
                            @for (int i = 0; i < Model.Roles.Count; i++)
                            {
                                <tr>
                                    <td data-id="@Model.Roles[i].RoleId" class="gp-role-name">
                                        @Model.Roles[i].RoleId
                                        @Html.HiddenFor(m => m.Roles[i].RoleId)
                                        @Html.HiddenFor(m => m.Roles[i].Name)
                                        @Html.HiddenFor(m => m.Roles[i].HireRequestId)
                                    </td>
                                    @for (int j = 0; j < Model.Roles[i].Companies.Count; j++)
                                    {
                                        <td class="gp-company-checkbox">
                                            @Html.HiddenFor(m => m.Roles[i].Companies[j].CompanyId)
                                            @Html.HiddenFor(m => m.Roles[i].Companies[j].Name)
                                            @Html.CheckBoxFor(m => m.Roles[i].Companies[j].IsSelected)
                                        </td>
                                    }
                                </tr>
                            }
                        </tbody>
                    </table>

发布回发后，角色视图模型中的公司集合始终为空。我确定这是明显的，但我看不出我做错了什么。

回发行动中的代码非常冗长，因为我试图逐步完成它并弄清楚出了什么问题。