Question

我正在使用编辑器模板显示用户可以分配给的每个角色的复选框。该模型是：

public class UserModel
{
    [Required]
    [Display(Name = "User name")]
    public string UserName { get; set; }

    [Required]
    [DataType(DataType.EmailAddress)]
    [Display(Name = "Email address")]
    public string Email { get; set; }

    [Required]
    [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
    [DataType(DataType.Password)]
    [Display(Name = "Password")]
    public string Password { get; set; }

    [DataType(DataType.Password)]
    [Display(Name = "Confirm password")]
    [Compare("Password", ErrorMessage = "The password and confirmation password do not match.")]
    public string ConfirmPassword { get; set; }

    public IEnumerable<string> UserRoles { get; set; }
}
public class UserRoleModel
{
    public IEnumerable<RoleViewModel> AllRoles { get; set; }
    public UserModel user { get; set; }

    public UserRoleModel()
    {
        this.AllRoles = Roles.GetAllRoles().Select(r => new RoleViewModel
        {
            Name = r
        });
        this.user = new UserModel();
    }
}
public class RoleViewModel
{
    public string Name { get; set; }
    public bool Selected { get; set; }
}

控制器：

    public ActionResult Create()
    {
        return View(new UserRoleModel());
    }

    [HttpPost]
    public ActionResult Create(UserRoleModel model)
    {
        if (ModelState.IsValid)
        {
            MembershipCreateStatus createStatus;
            Membership.CreateUser(model.user.UserName, model.user.Password, model.user.Email, null, null, true, null, out createStatus);

            if (createStatus == MembershipCreateStatus.Success)
            {


                foreach (var r in model.AllRoles)
                {
                    if (r.Selected)
                    {
                        Roles.AddUserToRole(model.user.UserName, r.Name);
                    }
                }

                return RedirectToAction("Index", "Home");
            }
            else
            {
                ModelState.AddModelError("", ErrorCodeToString(createStatus));
            }
        }

        return View(model);
    }

观点：

@model BBmvc.Areas.Tools.Models.UserRoleModel


@using (Html.BeginForm()) {
@Html.ValidationSummary(true)
<fieldset>
    <legend>UserModel</legend>

    <div class="editor-label">
        @Html.LabelFor(model => model.user.UserName)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.user.UserName)
        @Html.ValidationMessageFor(model => model.user.UserName)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.user.Email)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.user.Email)
        @Html.ValidationMessageFor(model => model.user.Email)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.user.Password)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.user.Password)
        @Html.ValidationMessageFor(model => model.user.Password)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.user.ConfirmPassword)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.user.ConfirmPassword)
        @Html.ValidationMessageFor(model => model.user.ConfirmPassword)
    </div>
    <div class="editor-field">
        @Html.EditorFor(x => x.AllRoles)
    </div>


    <p>
        <input type="submit" value="Create" />
    </p>
</fieldset>

}

和编辑器模板

    @model BBmvc.Areas.Tools.Models.RoleViewModel
@Html.CheckBoxFor(x => x.Selected)
@Html.LabelFor(x => x.Selected, Model.Name)
@Html.HiddenFor(x => x.Name)
<br />

问题在于，无论是否选中任何复选框，后期操作都没有区别。它似乎不会以某种方式与模型绑定。

Answer 1

您的问题来自延迟执行LINQ查询。您需要急切地初始化集合：

public class UserRoleModel
{
    public IEnumerable<RoleViewModel> AllRoles { get; set; }
    public UserModel user { get; set; }

    public UserRoleModel()
    {
        this.AllRoles = Roles.GetAllRoles().Select(r => new RoleViewModel
        {
            Name = r
        }).ToList();
        this.user = new UserModel();
    }
}

请注意.ToList()来电：

this.AllRoles = Roles.GetAllRoles().Select(r => new RoleViewModel
{
    Name = r
}).ToList();

这是解释。当你写：

this.AllRoles = Roles.GetAllRoles().Select(r => new RoleViewModel
{
    Name = r
});

此时查询未执行。仅构建表达式树，但仅当某些内容开始迭代集合时才执行实际查询。什么开始迭代？首先是它的观点。在视图中，您使用此集合的编辑器模板：

@Html.EditorFor(x => x.AllRoles)

由于AllRoles是一个集合属性，因此ASP.NET MVC将自动迭代并呈现集合中每个元素的编辑器模板。所以这适用于正确渲染视图。

现在让我们看一下表单发布时会发生什么。您发布到Create操作并且默认模型绑定器启动。调用构造函数但是由于没有任何内容可以迭代AllRoles属性，因此此时不执行查询。实际上它会在动作中执行，并且值会丢失。

出于这个原因，我建议你不要在构造函数中初始化视图模型。在相应的控制器操作中执行此操作会更好：

public class UserRoleModel
{
    public IEnumerable<RoleViewModel> AllRoles { get; set; }
    public UserModel user { get; set; }
}

然后：

public ActionResult Create()
{
    var model = new UserRoleModel
    {
        AllRoles = Roles.GetAllRoles().Select(r => new RoleViewModel
        {
            Name = r
        }).ToList(),
        user = new UserModel()
    };
    return View(model);
}

编辑器模板中的复选框未绑定到后期操作中的模型

1 个答案: