ASP.NET MVC模型绑定相同的实体在同一页 [英] ASP.NET MVC Model Binding Related Entities on Same Page

问题描述

这个问题一直让我疯狂了几个小时...

This problem has been driving me crazy for several hours now...

在我的域中，我有2个相互关联的实体 Sku 和项目。每个sku可以有很多项目。

In my domain, I have 2 entities that are related to each other Sku and Item. Each sku can have many items.

public class Sku
{
    private readonly EntitySet<Item> items;
    public Sku()
    {
        items = new EntitySet<Item>(AttachItems, DetachItems);
    }
    public int SkuId { get; set; }
    public string LongDescription { get; set; }
    public EntitySet<Item> Items
    {
        get { return items; }
        set{ items.Assign(value);}
    }
    private void AttachItems(Item entity)
    {
        entity.Sku = this;
    }
    private static void DetachItems(Item entity)
    {
        entity.Sku = null;
    }
}

public class Item
{
    public Sku Sku { get; set; }
    public int ItemId { get; set; }
    public string Category { get; set; }
    public string Description { get; set; }
}

我正在构建一个页面，允许最终用户更新一些

I am building a page that will allow the end-user to update some fields on the sku and some fields on each item at the same time.

<% using (Html.BeginForm("Save", "Merchant", FormMethod.Post, 
       new { enctype = "multipart/form-data" })) { %>       
<fieldset>
    <legend>Sku</legend>
    <p><label for="SkuId">SkuId:</label>
       <%= Html.TextBox("SkuId", Model.SkuId, 
           new{@readonly="readonly",onfocus="this.blur();"}) %></p>
    <p><label for="LongDescription">LongDescription:</label>
       <%= Html.TextBox("LongDescription", Model.LongDescription) %></p>
</fieldset>
<% for (int i = 0; i < Model.Items.Count; i++) { %>       
<fieldset>
    <legend>Item</legend>
    <p><label for="ItemId">ItemId:</label>
       <%= Html.TextBox(string.Format("items[{0}].{1}", i, "ItemId"), 
           Model.Items[i].ItemId, 
           new { @readonly = "readonly", onfocus = "this.blur();" })%></p>
    <p><label for="Category">Category:</label>
       <%= Html.TextBox(string.Format("items[{0}].{1}", i, "Category"), 
           Model.Items[i].Category)%></p>
    <p><label for="Description">Description:</label>
       <%= Html.TextBox(string.Format("items[{0}].{1}", i, "Description"), 
           Model.Items[i].Description)%></p>
</fieldset>
<%} // for-loop %>
    <p><input type="submit" value="Save" /></p>
<%} // form %> 

我有一些控制器代码，通过接受 Sku 和 EntitySet 项目，然后分配项目到 Sku 。

I have some controller code that works by accepting both a Sku and an EntitySet of Item and then assigning the Items to the Sku.

    [AcceptVerbs(HttpVerbs.Post)]
    public ActionResult Save(Sku sku, EntitySet<Item> items)
    {
        if (sku != null)
        {
            if (items != null)
            {
                sku.Items.Assign(items);
            }
        }

        // save Sku to repository ...
        // return Details view ...
    }

但是，我注意到，通过 DefaultModelBinder 每个项目除了 Sku 之外的一次旅行。当 Sku 被绑定时，调用项目的设置器，粘合剂甚至通过水合项目集合与正确的值。但是，在调用 items.Assign 之后， Items.Count 是 0 。这就是为什么我必须重新分配控制器代码中的项目。我期待的项目被转移到绑定工具的项目集合。这样可以消除每个项目额外的行程，因为我的控制器方法上的项目参数可以被删除。为什么这不工作？

This works, however I have noticed that it makes two trips through the DefaultModelBinder for each Item in addition to one trip for the Sku. When the Sku is bound, the setter for Items is called, and the binder even passes in a hydrated Items collection with the correct values. However, after the call to items.Assign, Items.Count is 0. This is why I have to re-assign the items in the controller code. I was expecting the items to be transferred over to the Items collection by the binder. This should eliminate the extra trip per item, since the items parameter on my controller method could be removed. Why isn’t this working?

推荐答案

您可能需要为此创建自定义模型binder？

You might need to create a custom model binder for this?

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