ASP.NET MVC2 中嵌套属性的 UpdateModel

Question

我目前正在以个人项目的形式第二次学习 MvcMusicStore 教程。这次我尝试使用 nHibernate 和一些使用 Castle Windsor 的 IoC，而不是实体框架。

我遇到的第一个障碍与嵌套类和模型绑定有关。我能够显示专辑列表，然后对其进行编辑。只要我编辑 Title、Price 或 AlbumArtUrl 字段，我还能够持久保存对数据库的更改。当我尝试编辑 Artist 或 Genre 字段时，会出现以下错误。

“'MvcMusicStore.Models.Album' 类型的模型无法更新。”

此错误发生在对 UpdateModel 的调用中，因此我假设它与绑定有关，但我完全不知道如何继续。从我在 StackOverflow 和其他地方进行的搜索来看，这似乎是一个常见问题，但到目前为止我还没有找到解决方案。

我希望有人能发现我在这里做错了什么并提出解决方案。

专辑

public class Album
{
    public virtual int AlbumId { get; set; }
    public virtual Artist Artist { get; set; }
    public virtual Genre Genre { get; set; }
    public virtual string Title { get; set; }
    public virtual decimal Price { get; set; }
    public virtual string AlbumArtUrl { get; set; }
}

StoreManagerViewModel

public class StoreManagerViewModel
{
    public Album Album { get; set; }
    public IList<Artist> Artists { get; set; }
    public IList<Genre> Genres { get; set; }
}

编辑.aspx

<%@ Page Language="C#" MasterPageFile="/Views/Shared/Site.Master" 
   Inherits="System.Web.Mvc.ViewPage<MvcMusicStore.ViewModels.StoreManagerViewModel>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
    Edit - <%: Model.Album.Title %>
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

    <h2>Edit Album</h2>

    <% using (Html.BeginForm()) {%>
        <%: Html.ValidationSummary(true) %>

    <fieldset>
        <legend>Edit Album</legend>
        <%: Html.EditorFor(model => model.Album, 
            new { Artists = Model.Artists, Genres = Model.Genres}) %>

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

    <% } %>

    <div>
        <%: Html.ActionLink("Back to List", "Index") %>
    </div>

</asp:Content>

专辑.ascx

<%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<MvcMusicStore.Models.Album>" %>

<div class="editor-label">
    <%: Html.LabelFor(model => model.Title) %>
</div>
<div class="editor-field">
    <%: Html.TextBoxFor(model => model.Title) %>
    <%: Html.ValidationMessageFor(model => model.Title) %>
</div>

<div class="editor-label">
    <%: Html.LabelFor(model => model.Price) %>
</div>
<div class="editor-field">
    <%: Html.TextBoxFor(model => model.Price, String.Format("{0:F}", Model.Price)) %>
    <%: Html.ValidationMessageFor(model => model.Price) %>
</div>

<div class="editor-label">
    <%: Html.LabelFor(model => model.AlbumArtUrl) %>
</div>
<div class="editor-field">
    <%: Html.TextBoxFor(model => model.AlbumArtUrl) %>
    <%: Html.ValidationMessageFor(model => model.AlbumArtUrl) %>
</div>

<div class="editor-label">
    <%: Html.LabelFor(model => model.Artist)%>
</div>
<div class="editor-field">
    <%: Html.DropDownListFor(model => model.Artist, new SelectList(ViewData["Artists"] as IEnumerable, "ArtistId", "Name", Model.Artist))%>
</div>

<div class="editor-label">
    <%: Html.LabelFor(model => model.Genre)%>
</div>
<div class="editor-field">
    <%: Html.DropDownListFor(model => model.Genre, new SelectList(ViewData["Genres"] as IEnumerable, "GenreId", "Name", Model.Genre))%>
</div>

StoreManagerController

    public ActionResult Edit(int id)
    {
        var viewModel = new StoreManagerViewModel
        {
            Album = AlbumRepository.GetById(id),
            Genres = GenreRepository.GetAll().ToList(),
            Artists = ArtistRepository.GetAll().ToList(),
        };

        return View(viewModel);
    }

    [HttpPost, UnitOfWork]
    public ActionResult Edit(int id, FormCollection formValues)
    {
        var album = AlbumRepository.GetById(id);

        try
        {
            UpdateModel(album, "Album");
            AlbumRepository.SaveOrUpdate(album);

            return RedirectToAction("Index");
        }
        catch
        {
            var viewModel = new StoreManagerViewModel
            {
                Album = album,
                Genres = GenreRepository.GetAll().ToList(),
                Artists = ArtistRepository.GetAll().ToList(),
            };

            return View(viewModel);
        }
    }

更新 1：

如果我在 UpdateModel 处断点并查看 ValueProvider.GetValue("Album.Artist")，我可以看到更新后的 ArtistId。这表明我完全误解了这应该如何工作。

我真的应该让 UpdateModel 处理它可以这样处理的属性吗：

UpdateModel(album, "Album", new string[] { "Title", "Price", "AlbumArtUrl" });

然后通过自己根据 ValueProvider 中的 ArtistId、GenreId 获取对象来手动更新 Artist 和 Genre 属性？

更新 2

某种修复？

专辑.ascx

<div class="editor-label">
    <%: Html.LabelFor(model => model.Artist)%>
</div>
<div class="editor-field">
    <%: Html.DropDownListFor(model => model.Artist, new SelectList(ViewData["Artists"] as IEnumerable, "ArtistId", "Name", Model.Artist.ArtistId))%>
</div>

<div class="editor-label">
    <%: Html.LabelFor(model => model.Genre)%>
</div>
<div class="editor-field">
    <%: Html.DropDownListFor(model => model.Genre, new SelectList(ViewData["Genres"] as IEnumerable, "GenreId", "Name", Model.Genre.GenreId))%>
</div>

StoreManagerController

UpdateModel(album, "Album", new string[] { "Title", "Price", "AlbumArtUrl" });
album.Artist = ArtistRepository.GetById(Int32.Parse(formValues["Album.Artist"]));
album.Genre = GenreRepository.GetById(Int32.Parse(formValues["Album.Genre"]));
AlbumRepository.SaveOrUpdate(album);

这行得通，我不知道这种事情应该怎么做。如果不是这样，我会很感激有人让我正确吗？

Answer 1

你必须在UpdateModel()中提供你的逻辑

此外，如果您有强类型视图，您可以将模型用作控制器参数，而不是 FormCollection。排除已编辑专辑的 id 也是一个好习惯。

ActionResult Edit([Bind(Exclude = "AlbumId")]Album album)

您将在相册中获取表单中的所有字段进行编辑。

关于您的代码：
现在我在您的代码中看到您通过 id 当前专辑在您的数据库中获得

 var album = AlbumRepository.GetById(id);

然后尝试用它做一些动作，不清楚你是如何从视图中绑定信息的。

Answer 2

为了解决这个问题，我在 ViewModel 中创建了一个属性，该属性链接到相关对象，然后绑定到该属性：

---

型号

public class User
{
    [Required(ErrorMessage = "Your first name is required.")]
    public string FirstName { get; set; }

    [Required(ErrorMessage = "Your last name is required.")]
    public string LastName { get; set; }        


    [Required(ErrorMessage = "A logon name is required.")]
    public string Logon { get; set; }

    [Required(ErrorMessage = "A password is required.")]
    public string Password { get; set; }

    [Required(ErrorMessage = "A role is required.")]
    public string Role { get; set; }

    [Required(ErrorMessage = "An airport is required.")]
    public Airport Airport { get; set; }

    [DisplayName("Is Active")]
    bool IsActive { get; set; }
}

查看

       <div class="form-field">
            <div class="field-label"><%= Html.LabelFor(m => m.User.Airport) %>:</div>
            <div class="field-input"><%= Html.DropDownListFor(m => m.UserAirportId, new SelectList(Model.Airports, "Id", "Name"))%></div>
            <div class="field-result"><%= Html.ValidationMessageFor(m => m.User.Airport) %></div>
        </div> 

视图模型

    public class UserViewModel
{
    public User User { get; set; }
    public List<Airport> Airports { get; set; }
    public List<String> Roles { get; set; }

    //Hack to get around non-binding of complex objects by UpdateModel
    public Guid UserAirportId
    {
        get
        {
            if (User != null && User.Airport != null)
                return User.Airport.Id;

            return Guid.Empty;
        }

        set
        {
            if (User == null)
                return;

            var airport = Airports.Where(m => m.Id == value).FirstOrDefault();

            if (airport == null)
                return;

            User.Airport = airport;
        }
    }
}