由于 PartialView 之后 ModelState 丢失，MVC 3 验证消息未显示

Question

我有一个 MVC 3 项目，其中有 1 个视图 LoginRegister，其中包含 2 个带有登录和预注册表单的视图。问题是在错误地完成预注册表单并使用 PartialView("LoginRegister", loginRegisterViewModel) 后，由于 ModelState 丢失，验证消息不会显示。在阅读下一段之前，最好跳到代码。

调试 PartialView("LoginRegister", loginRegisterViewModel) 并进入 PreRegister 视图，查看以下 @Html.ErrorMessageFor(model => model.Email)。其中 ModelState 不包含电子邮件密钥（见下文），因此不会显示错误消息。

    private static MvcHtmlString ErrorMessageHelper(this HtmlHelper htmlHelper, ModelMetadata modelMetadata, string expression, string validationMessage, IDictionary<string, object> htmlAttributes)
    {
        string modelName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(expression);

        if (!htmlHelper.ViewData.ModelState.ContainsKey(modelName)) // ModelState contains no keys, e.g. Email not found and a null is returned
        {
            return null; 
        }

        // code continues here to render error message
    }

代码

ViewModels

LoginRegisterViewModel

namespace Site.ViewModels.Account
{
    public class LoginRegisterViewModel
    {
        public bool IsDialog { get; set; }
        public PreRegisterViewModel PreRegister { get; set; }
        public QuickLoginViewModel QuickLogin { get; set; }
    }
}

PreRegisterViewModel

using FluentValidation.Attributes;
using Site.ViewModels.Validators;

namespace Site.ViewModels.Account
{
    [Validator(typeof(PreRegisterViewModelValidator))]
    public class PreRegisterViewModel
    {
        public string Email { get; set; }
        public string ConfirmEmail { get; set; }
    }
}

视图

LoginRegister

@model Site.ViewModels.Account.LoginRegisterViewModel

@{
    Layout = ViewBag.Layout;
}

<div id="loginReg" class="mod-loginReg">
    <h2>Login and Registration</h2>
    @{Html.RenderPartial("PreRegister", Model.PreRegister, new ViewDataDictionary());}
    @{Html.RenderPartial("QuickLogin", Model.QuickLogin, new ViewDataDictionary());}
</div>

PreRegister

@using Site.Classes.MVC.Extensions;

@model Site.ViewModels.Account.PreRegisterViewModel

@using (Html.BeginForm("PreRegister", "Account", FormMethod.Post, new { @class = "form-errorContainer" }))
{
    <div class="mod-loginReg-register">
        <h3>Register</h3>
        <p>Please enter your email address to register.<br /><br /></p>

        <div class="mod-loginReg-form">
            <div class="field-item">
                @Html.LabelFor(model => model.Email)
                @Html.TextBoxFor(model => model.Email, new { @maxlength = "255", @class = "Textbox required email" })
                @Html.ErrorMessageFor(model => model.Email)
            </div>
            <div class="field-item">
                @Html.LabelFor(model => model.ConfirmEmail)
                @Html.TextBoxFor(model => model.ConfirmEmail, new { @maxlength = "255", @class = "Textbox required email" })
                @Html.ErrorMessageFor(model => model.ConfirmEmail)
            </div>
            <div class="button-group">
                @Html.Button("Register", "Register")
            </div>
        </div>
    </div>
}

<强>帐户控制器

    [RequireHttps]
    public ActionResult LoginRegister(int showDialog)
    {
        var loginRegisterViewModel = new LoginRegisterViewModel();

        if (showDialog == 1)
        {
            ViewBag.Layout = "~/layouts/structure/dialog.cshtml";
            loginRegisterViewModel.IsDialog = true;
        }
        else
        {
            ViewBag.Layout = "~/layouts/structure/2column.cshtml";
        }

        return PartialView(loginRegisterViewModel);
    }

    [RequireHttps]
    public ActionResult PreRegister()
    {
        return PartialView();
    }

    [HttpPost]
    [RequireHttps]
    public ActionResult PreRegister(PreRegisterViewModel model)
    {
        if (ModelState.IsValid)
        {
            return PartialView("PreRegisterComplete");
        }

        var loginRegisterViewModel = new LoginRegisterViewModel { PreRegister = model, QuickLogin = new QuickLoginViewModel() };

        return PartialView("LoginRegister", loginRegisterViewModel);
    }

Answer 1

这是由于调用 new ViewDataDictionary() 时 viewData 被清除所致。

@{Html.RenderPartial("PreRegister", Model.PreRegister, new ViewDataDictionary());}
@{Html.RenderPartial("QuickLogin", Model.QuickLogin, new ViewDataDictionary());}

根据 MSDN ViewDataDictionary 用于：

表示一个容器，用于在控制器之间传递数据
和一个视图。

我认为您对此有充分的理由，否则您不会不厌其烦地添加附加参数。

如果将其更改为：

@Html.RenderPartial("PreRegister", Model.PreRegister)
@Html.RenderPartial("QuickLogin", Model.QuickLogin)

控制器中构建的 ModelState 应该在您的视图上可用。