Question

我遇到的问题是虽然AssignedUsers属性在我的构造函数中初始化（在离开GET Edit之前），但在提交表单后，它在POST Edit操作中返回为null。所有其他财产保持其状态。

除了在ModelState.IsValid检查之后（以及在返回View之前）重新初始化属性之外，还有其他方法可以解决这个问题吗？

型号：

 public class GroupModel {

    public List<int> AssignedUserIds { get; set; }

    public MultiSelectList AssignedUsers { get; set; }

    public GroupModel(Groups group) {
        var allUserGroups = AccountManagementAdapter.GetUserGroups();

        AssignedUsers = new MultiSelectList(
            allUserGroups
            .Where(userGroup => userGroup.GroupId == Id)
            .Select(userGroup => userGroup.Users)
            .ToList(),
            "Id",
            "Username");

        AssignedUserIds = allUserGroups
             .Where(userGroup => userGroup.GroupId == Id)
             .Select(userGroup => userGroup.UserId)
             .ToList();
    }

查看：

@using (Html.BeginForm()) {
@Html.ListBoxFor(group => group.AssignedUserIds, Model.AssignedUsers)
<input type="submit" value="Save"/>
}

控制器：

    [HttpGet]
    public ActionResult Edit(int id) {
        GroupModel groupModel = new GroupModel(AccountManagementAdapter.GetGroups().FirstOrDefault(group => group.Id == id));
        return View(groupModel);
    }

    [HttpPost]
    public ActionResult Edit(GroupModel group) {
        if (ModelState.IsValid) {
            group = new GroupModel(AccountManagementAdapter.UpdateUsersForGroup(group.Id, group.AssignedUserIds));
            ViewBag.Success = true;
        }

        return View(group);
    }

Answer 1

您不是在表单中发布数据。所以它不会被返回到编辑方法。您应该采用哪种方式，我不建议将数据发布到您的表单。

我会做这样的改变

型号：

 public class GroupModel {

    public List<int> AssignedUserIds { get; set; }

    MultiSelectList _assignedUsers;
    public MultiSelectList AssignedUsers () {
       return _assignedUsers ?? _assignedUsers = new MultiSelectList(
            AllUserGroups
            .Where(userGroup => userGroup.GroupId == Id)
            .Select(userGroup => userGroup.Users)
            .ToList(),
            "Id",
            "Username");
    }
    private object _allUserGroups; /* not sure what this is */
    private object AllUserGroups {
          get { return _allUserGroups ?? _allUserGroups = AccountManagementAdapter.GetUserGroups();
    }

    public GroupModel(Groups group) {
           AssignedUserIds = AllUserGroups
                 .Where(userGroup => userGroup.GroupId == Id)
                 .Select(userGroup => userGroup.UserId)
                 .ToList();
   }

查看：

@Html.ListBoxFor(group => group.AssignedUserIds, Model.AssignedUsers())

或你可以这样做

public class GroupModel {

    public List<int> AssignedUserIds { get; set; }

    public MultiSelectList AssignedUsers { get; set; }

    private object allUserGroups
    public GroupModel() {
        allUserGroups = AccountManagementAdapter.GetUserGroups();
        AssignedUsers = new MultiSelectList(
            allUserGroups
            .Where(userGroup => userGroup.GroupId == Id)
            .Select(userGroup => userGroup.Users)
            .ToList(),
            "Id",
            "Username");
    }
    public GroupModel(Groups group) :this() {
        AssignedUserIds = allUserGroups
             .Where(userGroup => userGroup.GroupId == Id)
             .Select(userGroup => userGroup.UserId)
             .ToList();
    }

提交POST后，MVC 4模型绑定属性丢失

1 个答案: