asp.net-mvc - ASP.NET MVC 中具有动态数量文本框的表单

Question

考虑以下模型和 Controller :

public class SimpleModel
{
    [Required(ErrorMessage="Email Address is required.")]
    [DataType(DataType.EmailAddress)]
    [DisplayName("EmailAddress")]
    public string EmailAddress { get; set; }
}

[HandleError]
public class SimpleController : Controller
{
    public ActionResult Simple()
    {
        return View();
    }

    [HttpPost]
    public ActionResult Simple(SimpleModel model)
    {
        if (ModelState.IsValid)
        {
            // handling code here
        }

        return View(model);
    }
}

...以及匹配 View 中的相关部分:

    <% using (Html.BeginForm()) { %>
    <%= Html.ValidationSummary(true, "The form submitted is not valid.") %>
    <div> 
        <fieldset>
            <div class="editor-label">
                <%= Html.LabelFor(m => m.EmailAddress)%>
            </div>
            <div class="editor-field">
                <%= Html.TextBoxFor(m => m.EmailAddress)%>
                <%= Html.ValidationMessageFor(m => m.EmailAddress)%>
            </div>

            <div class="editor-field">
                <input type="submit" value="Submit" />
            </div>
        </fieldset>
    </div>
<% } %>

修改模型、 View 和 Controller 以支持 Controller 定义的动态电子邮件地址数量的最佳方法是什么。

Answer 1

基于 Steve Sanderson 的文章我找到了我正在寻找的优雅解决方案:

首先需要对模型进行如下修改:

public class SimpleModel
{
    public IEnumerable<EmailAddress> EmailAddresses { get; set; }
}

public class EmailAddress
{
    [Required(ErrorMessage = "Email Address is required.")]
    [DataType(DataType.EmailAddress)]
    [DisplayName("Email Address")]
    public string Value { get; set; }        
}

处理 GET 方法的 Controller 方法需要使用所需数量的条目预先填充模型:

[HandleError]
public class SimpleController : Controller
{
    public ActionResult Simple()
    {
        SimpleModel model = new SimpleModel
            {
                EmailAddresses =
                    new List<EmailAddress>
                        { 
                            // as many as required
                            new EmailAddress { Value = string.Empty }, 
                            new EmailAddress { Value = string.Empty },
                            new EmailAddress { Value = string.Empty }
                        }
            };
        return View(model);
    }

    [HttpPost]
    public ActionResult Simple(SimpleModel model)
    {
        if (ModelState.IsValid)
        {
            // handling code here
        }

        return View(model);
    }
}

View 也需要更改:

    <% using (Html.BeginForm()) { %>
    <%= Html.ValidationSummary(true, "The form submitted is not valid.") %>
    <div> 
        <fieldset>
            <% foreach (var item in Model.EmailAddresses)
                   Html.RenderPartial("SimpleRows", item);
             %>

            <div class="editor-field">
                <input type="submit" value="Submit" />
            </div>

        </fieldset>
    </div>
<% } %>

...并且需要创建一个新的局部 View 。请注意，该 View 与集合项的类型是强类型的。

<% using(Html.BeginCollectionItem("EmailAddresses")) { %>
<div class="editor-label">
    <%= Html.LabelFor(x => x.Value)%>
</div>
<div class="editor-field">
    <%= Html.TextBoxFor(x => x.Value)%>
    <%= Html.ValidationMessageFor(x => x.Value)%>
</div>
<% }%>

BeginCollectionItem 是 Sanderson 创建的一个 Helper 方法:

    public static class HtmlPrefixScopeExtensions
{
    private const string idsToReuseKey = "__htmlPrefixScopeExtensions_IdsToReuse_";

    public static IDisposable BeginCollectionItem(this HtmlHelper html, string collectionName)
    {
        var idsToReuse = GetIdsToReuse(html.ViewContext.HttpContext, collectionName);
        string itemIndex = idsToReuse.Count > 0 ? idsToReuse.Dequeue() : Guid.NewGuid().ToString();

        // autocomplete="off" is needed to work around a very annoying Chrome behaviour whereby it reuses old values after the user clicks "Back", which causes the xyz.index and xyz[...] values to get out of sync.
        html.ViewContext.Writer.WriteLine(string.Format("<input type=\"hidden\" name=\"{0}.index\" autocomplete=\"off\" value=\"{1}\" />", collectionName, html.Encode(itemIndex)));

        return BeginHtmlFieldPrefixScope(html, string.Format("{0}[{1}]", collectionName, itemIndex));
    }

    public static IDisposable BeginHtmlFieldPrefixScope(this HtmlHelper html, string htmlFieldPrefix)
    {
        return new HtmlFieldPrefixScope(html.ViewData.TemplateInfo, htmlFieldPrefix);
    }

    private static Queue<string> GetIdsToReuse(HttpContextBase httpContext, string collectionName)
    {
        // We need to use the same sequence of IDs following a server-side validation failure,  
        // otherwise the framework won't render the validation error messages next to each item.
        string key = idsToReuseKey + collectionName;
        var queue = (Queue<string>)httpContext.Items[key];
        if (queue == null) {
            httpContext.Items[key] = queue = new Queue<string>();
            var previouslyUsedIds = httpContext.Request[collectionName + ".index"];
            if (!string.IsNullOrEmpty(previouslyUsedIds))
                foreach (string previouslyUsedId in previouslyUsedIds.Split(','))
                    queue.Enqueue(previouslyUsedId);
        }
        return queue;
    }

    private class HtmlFieldPrefixScope : IDisposable
    {
        private readonly TemplateInfo templateInfo;
        private readonly string previousHtmlFieldPrefix;

        public HtmlFieldPrefixScope(TemplateInfo templateInfo, string htmlFieldPrefix)
        {
            this.templateInfo = templateInfo;

            previousHtmlFieldPrefix = templateInfo.HtmlFieldPrefix;
            templateInfo.HtmlFieldPrefix = htmlFieldPrefix;
        }

        public void Dispose()
        {
            templateInfo.HtmlFieldPrefix = previousHtmlFieldPrefix;
        }
    }
}

...就是这样...当您发布表单时，模型将自动填充并传递给处理 POST 方法的 Controller 操作。

请注意，使用此解决方案，包括验证在内的所有属性都按预期工作。