c# - 为什么 MVC 不绑定(bind)我的嵌套集合？

Question

如果我尝试通过表单编辑几个 linqTOsql 对象。

首先是 Stream 类:

[Table]
public class Stream
{
    [HiddenInput(DisplayValue = false)]
    [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
    public long StreamID { get; set; }

    /*other properties removes for brevity*/

    // relationship (one stream to many Stream2FieldTypes) 
    // uses EntitySet<Stream2FieldTypes> and OtherKey for the FK in Stream2FieldTypes 
    private EntitySet<Stream2FieldTypes> _Stream2FieldTypes;
    [System.Data.Linq.Mapping.Association(Storage = "_Stream2FieldTypes", OtherKey = "StreamID")]
    public EntitySet<Stream2FieldTypes> Stream2FieldTypes
    {
        get { return this._Stream2FieldTypes; }
        set { this._Stream2FieldTypes.Assign(value); }
    }

}

然后是 Stream2FieldTypes 类:

[Table]
public class Stream2FieldTypes
{
    [Column(IsPrimaryKey = true, IsDbGenerated = true, AutoSync = AutoSync.OnInsert)]
    public long s2fID { get; set; }

    /*other properties removed for brevity*/

    [Column]
    public long StreamID { get; set; }     // FK




    // relationship (one Stream2FieldTypes to Streams) 
    private EntitySet<Stream> _Stream;
    [Association(Storage = "_Stream", ThisKey = "StreamID")]
    public EntitySet<Stream> Stream
    {
        get { return this._Stream; }
        set { this._Stream.Assign(value); }
    }
}

我使用 linqTOsql 存储库获取这些对象并将它们发送到 View ，如下所示:

    public ActionResult StreamEdit(long id)
    {
        Genesis.Domain.Entities.Stream stream = genesisRepository.Streams.FirstOrDefault(x => x.StreamID == id);

        return View(stream);
    }

一切都毫无问题地发送到 View ...但是当提交 View 上的表单时，Stream.Stream2FieldTypes 由于某种原因丢失了。我通过此操作捕获了表单提交:

    [HttpPost]
    public ActionResult StreamEdit( long id, Genesis.Domain.Entities.Stream form)
    {

            return View(form);
    }

并且该 View 没有 Stream2FieldTypes 集合。

View 正在像这样编写 Stream2FieldTypes:

<% for (int i = 0; i < (Model.Stream2FieldTypes != null ? Model.Stream2FieldTypes.Count() : 0); i++) %>
<% { %>
    <div class="ListItem">
        Label: <%: Html.EditorFor(x => x.Stream2FieldTypes[i].s2fLabel, new { style="width:100px" })%>
        Required: <%: Html.EditorFor(x => x.Stream2FieldTypes[i].s2fIsRequired)%>
        Field Type ID": <%: Html.EditorFor(x => x.Stream2FieldTypes[i].FieldTypeID, new { style="width:20px;" })%>
        Stream ID: <%: Html.EditorFor(x => x.Stream2FieldTypes[i].StreamID) %>
</div>
<% } %>

为什么 mvc 中的默认模型绑定(bind)器不能正确绑定(bind)嵌套集合？

Answer 1

我建议您使用 POCO View 模型，而不是那些困惑的模型类。他们不适应这种观点，很难与之合作。尝试绑定(bind)到 LINQ 特定集合，如 EntitySet<T>这不是一个好主意。使用编辑器模板可能确实可行，但即使可行，请记住它应该是一个临时解决方案，直到您引入适当的 View 模型。

在您的主视图中用这个替换循环:

<%: Html.EditorFor(x => x.Stream2FieldTypes) %>

然后在 ~/Views/Home/EditorTemplates/Stream2FieldTypes.ascx 中添加强类型分部 View :

<%@ Control 
    Language="C#" 
    Inherits="System.Web.Mvc.ViewUserControl<SomeNs.Stream2FieldTypes>" 
%>
<div class="ListItem">
    Label: 
    <%: Html.EditorFor(x => x.s2fLabel, new { style="width:100px" }) %>

    Required: 
    <%: Html.EditorFor(x => x.s2fIsRequired) %>

    Field Type ID: 
    <%: Html.EditorFor(x => x.FieldTypeID, new { style="width:20px;" })%>

    Stream ID: 
    <%: Html.EditorFor(x => x.StreamID) %>
</div>

通常这应该负责生成正确的输入名称，但为了避免人们将此作为一个很好的例子:我再次重复使用正确的 View 模型。