ModelBinding绑定SelectedItem

Question

如何使用ModelBinding将SelectedItem绑定到我的模型？

首先，我创建了一个简单的模型：

public class Element
{
    public string Name { get; set; }
    public int Value { get; set; }
}
public class MyModel
{
    public Guid ContactID { get; set; }
    public List<Element> Collection { get; set; }

    public IEnumerable<SelectListItem> SelectList
    {
        get
        {
            return Collection.Select
            (
                e => new SelectListItem
                {
                    Text = e.Name,
                    Value = e.Value.ToString()
                }
            );
        }
    }

    public Element SelectedElement { get; set; }

}

然后在我的控制器中初始化它：

    public ActionResult Test()
    {
        var model = new MyModel {ContactID = Guid.NewGuid(), Collection = new List<Element>() };
        var rand = new Random();

        while (model.Collection.Count < 10)
        {
            var number = rand.Next(100);
            model.Collection.Add(new Element {Value = number, Name = number.ToString()});
        }

        return View(model);
    }

并在我的视图中显示它：

@using (Html.BeginForm("TestPostBack", "Home"))
{
    @Html.AntiForgeryToken()

<div class="form-horizontal">
    <h4>MyModel</h4>
    <hr />
    @Html.ValidationSummary(true, "", new { @class = "text-danger" })
    <div class="form-group">
        @Html.LabelFor(model => model.ContactID, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.ContactID, new { htmlAttributes = new { @class = "form-control" } })
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.Collection, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.DropDownListFor(model => model.SelectedElement, Model.SelectList)
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Save" class="btn btn-default" />
        </div>
    </div>
</div>
}

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

当按下表单上的submit按钮时，我想按下控制器上的TestPostBack。这也没问题。但是如何在我的模型中填充SelectedElement属性呢？我希望它是下拉列表中所选项目的值。

public ActionResult TestPostBack(MyModel model)
{
    throw new NotImplementedException();
}

Answer 1

我不认为获取整个对象会很简单。不是不可能，只是不容易。这里的问题是，与HTML select元素相对应的drop只返回选项的选定值，而不是文本。因此，您可能会想到截取表单post请求并在其中添加文本，但这感觉有点麻烦。

最直接的方法是只取回值：

public class MyModel
{
    ...
    public int SelectedElementValue { get; set; }
}

Html.DropDownListFor(model => model.SelectedElementValue, Model.SelectList)

然后通过值在元素中查找对象。希望它的价值是独特的：

public ActionResult TestPostBack(MyModel model)
{
    // load list of elements
    Element selectedElement = //look up element by model.SelectedElementValue
}