ListBoxFor不显示所选项目

Question

我有这个ListBoxFor：

<div class="col-sm-12">
    <div class="form-group">
        @Html.LabelFor(m => m.RolesList.Roles)
        @Html.ListBoxFor(m => m.RolesList.RoleIds, new MultiSelectList(Model.RolesList.Roles, "Value", "Text", Model.RolesList.RoleIds), new { @class = "form-control col-sm-12 js-select2" })
        @Html.ValidationMessageFor(m => m.RolesList.RoleIds)
    </div>
</div>

加载页面时，我可以选择多个项目并将其保存到数据库中。但是，在编辑页面时，什么也没有选择。

这是列表框的视图模型

public class ApplicationMultiRolesDropdownListViewModel
{
    [Display(Name = "Roles")]
    public List<string> RoleIds { get; set; }
    public IEnumerable<SelectListItem> Roles { get; set; }
}

我不确定要显示所选项目还需要做什么。

这就是我的控制器的外观

DocumentFieldDetailsViewModel dfdvm = new DocumentFieldDetailsViewModel();
var rolesData = new List<SelectListItem>();
applicationRolesData.GetAll().ForEach(
    x => rolesData.Add(new SelectListItem
    {
        Value = x.RoleId,
        Text = x.RoleName + " (" + x.ApplicationName + ")"
    })
);
ApplicationMultiRolesDropdownListViewModel ardlvm = new ApplicationMultiRolesDropdownListViewModel();
ardlvm.Roles = new SelectList(rolesData, "Value", "Text");
var result = documentFieldsData.Get(Id);
var permissions = documentFieldPermissionsData.GetAll(result.Id);
ardlvm.RoleIds = permissions.Select(x => x.Id).ToArray();
dfdvm = new DocumentFieldDetailsViewModel
{
    DocumentCategoryId = DocumentCategoriesId,
    Id = Id,
    FieldName = result.Name,
    Order = result.Order,
    RolesList = ardlvm
};