MVC5 将项目添加到列表

Question

给定一个模型：

public class Receipt: BaseEntity
{
    [Required(AllowEmptyStrings = false,ErrorMessage = "Please Select A Store")]
    public Store  Store { get; set; }
    public List<Item> Items { get; set; }
    public Item NewItem { get; private set; }
    [Required(AllowEmptyStrings = false,ErrorMessage = "ReceiptModel.EntryDate is required")]
    public DateTime EntryDate { get; set; }
    public Guid EntryOwner { get; set; }
    public string Name { get; set; }

    public double ReceiptTotal()
    {
        return Items.Sum(item => item.ItemPrice);
    }
    public Receipt()
    {
        Items = new List<Item>();
        EntryOwner = Guid.Empty;
        EntryDate = DateTime.Now;
        Store = new Store();
        NewItem = new Item();
     }       
}

还有一个控制器：

public class ReceiptController : Controller
{
    //
    // GET: /Receipt/

    public ActionResult Index()
    {
        Receipt receipt = new Receipt();
        return View(receipt);
    }

    [HttpPost]
    public ActionResult AddItem(Receipt receipt)
    {
        receipt.Items.Add(receipt.NewItem);
        if (ModelState.IsValid)
        {
            return View("Index", receipt);
        }
        return View("Index", receipt);
    }

还有一个视图：更新的视图 - 删除了所有部分页面并合并为一个页面

<form class="form-horizontal" method="POST" action="@Url.Action("AddItem","Receipt")">
<div class="jumbotron">
    <div id="main" class="panel panel-primary">

        <div class="panel-heading"> <h1 class="panel-title">Receipt Builder</h1></div>
        <div class="panel-body">

            <fieldset>
                @Html.LabelFor(model => model.Name)
                @Html.EditorFor(model => model.Name)

                @Html.LabelFor(model => model.Store.Name)
                @Html.EditorFor(model => model.Store.Name)

                @Html.LabelFor(model => model.EntryDate)
                @Html.EditorFor(model => model.EntryDate)
            </fieldset>

        </div>


    </div>
</div>

<table class="table table-bordered table-condensed table-hover table-responsive table-striped">
    <thead>
        <tr>
            <td>
                <label class="control-label">#</label>
            </td>
            <td>
                <label class="control-label">Item</label>
            </td>
            <td>
                <label class="control-label">Unit</label>
            </td>
            <td>
                <label class="control-label">Quantity</label>
            </td>
            <td>
                <label class="control-label">UnitPrice</label>
            </td>
            <td>
                <label class="control-label">Category</label>
            </td>
            <td>
                <label class="control-label">Total</label>
            </td>
        </tr>
        <tr>

                <td>
                    <button class="btn-sm btn-danger" style="border-radius: 50%; background-color: red;" name="Submit" id="Submit" type="submit">+</button>
                </td>

                <td>
                    @Html.EditorFor(model => model.NewItem.Name)
                </td>

                <td>
                    @Html.EditorFor(model => model.NewItem.UnitType)
                </td>

                <td>
                    @Html.EditorFor(model => model.NewItem.Quantity)
                </td>

                <td>
                    @Html.EditorFor(model => model.NewItem.UnitPrice)
                </td>

                <td>
                    @Html.EditorFor(model => model.NewItem.Category.Name)<br/>
                    @Html.EditorFor(model => model.NewItem.Category.IsTaxable)
                </td>

                <td>
                    @Html.EditorFor(model => model.NewItem.ItemPrice)
                </td>


        </tr>
    </thead>
    <tbody>
        @foreach (var item in Model.Items)
        {
            <tr>
                <td>
                    @Model.Items.ToList().IndexOf(item) + 1
                </td>
                <td>
                    @Html.LabelFor(titem => item.Name)
                </td>
                <td>
                    @Html.LabelFor(titem => item.UnitType)
                </td>
                <td>
                    @Html.LabelFor(titem => item.Quantity)
                </td>
                <td>
                    @Html.LabelFor(titem => item.UnitPrice)
                </td>
                <td>
                    @Html.LabelFor(titem => item.Category.Name)
                </td>
                <td>
                    @Html.LabelFor(titem => item.ItemPrice)
                </td>
            </tr>
        }
    </tbody>

    <tfoot></tfoot>
</table>

Answer 1

感谢This Link，我终于能够解决这个问题

正如建议的那样，这确实是一个具有约束力的问题。似乎对于复杂的集合，例如 Lists，我们实际上不能像我希望的那样利用 IEnumerable 的好处。这是由于数据在名称不明确的帖子中实际传递的方式。这是工作的最终代码（只需要更新视图）

 @for (int i = 0; i < Model.Items.Count(); i++)
        {
            <tr>
                <td>
                @(i+1)
                </td>
                <td>
                    @Html.TextBoxFor(m => m.Items[i].Name)
                </td>
                <td>
                    @Html.TextBoxFor(m => m.Items[i].UnitType)
                </td>
                <td>
                    @Html.TextBoxFor(m => m.Items[i].Quantity)
                </td>
                <td>
                    @Html.TextBoxFor(m => m.Items[i].UnitPrice)
                </td>
                <td>
                    @Html.TextBoxFor(m => m.Items[i].Category.Name)
                </td>
                <td>
                    @Model.Items[i].ItemPrice
                </td>
            </tr>
        }

生成的 HTML 使用其索引命名每个元素，即 Item[N].Name 现在可以正确绑定post数据了。

Answer 2

收据中的项目仅以文本形式显示，没有控件。因此，当您将数据发布回服务器时，ASP.NET MVC 无法从请求正文中找到此信息，并将 Receipt.Items 集合留空。

您可以在 Html.HiddenFor() 方法的帮助下将有关输入收据的信息添加为部分视图中的隐藏字段。或者只是将输入的项目保存在数据库或其他地方，然后在返回 AddItem 视图之前将它们读入 Receipt.Items 集合。