asp.net-mvc-3 - DropDownListFor Unobtrusive Validation required 没有得到正确的属性

Question

This Question类似，但接受的答案解决了服务器端，我对客户端解决方案感兴趣。

鉴于此 ViewModel

public class MyViewModel
{
    public string ID { get; set; }

    [Required(ErrorMessage = "I DEMAND YOU MAKE A CHOICE!")]
    [Display(Name = "Some Choice")]
    public int SomeChoice{ get; set; }   
    [Required(ErrorMessage = "I DEMAND YOU MAKE A CHOICE!")]
    [Display(Name = "Keyword")]
    public string Keyword { get; set; }    
}

和 Razor

<div>
@Html.LabelFor(model => model.SomeChoice, new { @class = "label" })
@Html.DropDownListFor(model => model.SomeChoice, (SelectList)ViewBag.SomeChoice, "Select...")
@Html.ValidationMessageFor(model => model.SomeChoice)
</div>

并假设 ViewBag.SomeChoice 包含一个选择列表

呈现的 html 没有得到 data-val="true"data-val-required="I DEMAND YOU MAKE A CHOICE!"其中的属性，如 @Html.EditorFor(model => model.Keyword) 或 @Html.TextBoxFor 将呈现。

为什么？

像这样添加一个class =“required”

@Html.DropDownListFor(model => model.SomeChoice, (SelectList)ViewBag.SomeChoice, "Select...", new { @class = "required" })

它使用 jQuery Validation 类语义并在提交时阻止但不显示消息。我可以做这种事情

@Html.DropDownListFor(model => model.SomeChoice, (SelectList)ViewBag.SomeChoice, "Select...", new Dictionary<string, object> { { "data-val", "true" }, { "data-val-required", "I DEMAND YOU MAKE A CHOICE!" } })

它将把正确的属性放在那里，并阻止提交并显示消息，但没有利用我在 ViewModel 上的RequiredAttribute ErrorMessage

那么有没有人写过一个 DropDownListFor，它在验证方面的行为与其他 HtmlHelpers 一样？

编辑
这是我的确切代码

在 HomeController.cs

  public class MyViewModel
  {
    [Required(ErrorMessage = "I DEMAND YOU MAKE A CHOICE!")]
    [Display(Name = "Some Choice")]
    public int? SomeChoice { get; set; }
  }


    public ActionResult About()
    {
        var items = new[] { new SelectListItem { Text = "A", Value = "1" }, new SelectListItem { Text = "B", Value = "2" }, new SelectListItem { Text = "C", Value = "3" }, };
        ViewBag.SomeChoice = new SelectList(items,"Value", "Text");
        ViewData.Model = new MyViewModel {};
        return View();
    }

关于.cshtml

@using Arc.Portal.Web.Host.Controllers
@model MyViewModel
<script src="@Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>

@using (Html.BeginForm())
{
<div>
    @Html.LabelFor(model => model.SomeChoice)
    @Html.DropDownListFor(model => model.SomeChoice, (SelectList)ViewBag.SomeChoice, "Select...")
    @Html.ValidationMessageFor(model => model.SomeChoice)
</div>

<button type="submit">OK</button>
}

这是渲染的代码

<form action="/Home/About" method="post">    <div>
    <label for="SomeChoice">Some Choice</label>
    <select id="SomeChoice" name="SomeChoice"><option value="">Select...</option>
<option value="1">A</option>
<option value="2">B</option>
<option value="3">C</option>
</select>
    <span class="field-validation-valid" data-valmsg-for="SomeChoice" data-valmsg-replace="true">    </span>
</div>
<button type="submit">OK</button>
</form>

它发回给我的 Controller ......这不应该发生

Answer 1

只需在您将下拉列表绑定(bind)到 View 模型的属性上使用可为空的整数:

[Required(ErrorMessage = "I DEMAND YOU MAKE A CHOICE!")]
[Display(Name = "Some Choice")]
public int? SomeChoice { get; set; }  

此外，为了获得适当的不显眼的 HTML5 data-* 属性，下拉列表必须在表单内:

@model MyViewModel
<script src="@Url.Content("~/Scripts/jquery.validate.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.js")" type="text/javascript"></script>

@using (Html.BeginForm())
{
    <div>
        @Html.LabelFor(model => model.SomeChoice, new { @class = "label" })
        @Html.DropDownListFor(
            model => model.SomeChoice, 
            Model.ListOfChoices, 
            "Select..."
        )
        @Html.ValidationMessageFor(model => model.SomeChoice)
    </div>

    <button type="submit">OK</button>
}

你也会注意到我摆脱了 ViewBag (我根本无法忍受)并将其替换为 View 模型上的相应属性，该属性将包含下拉菜单的可能选项。