我有一个特殊的问题 – 我有一个带有List的ViewModel用于显示图像列表：

public List<int> TrackerKeys { get; set; }

这在页面的两个位置使用：

@for (int i = 0; i < Model.TrackerKeys.Count(); i++)
{ 
    @Html.GenerateImage(PageModes.Http, Model.TrackerKeys[i])
}

并且

@for (int i = 0; i < Model.TrackerKeys.Count(); i++)
{ 
    @Html.HiddenFor(model => model.TrackerKeys[i])
}

这是在表单中 – 当提交表单时,如果发生验证错误,则使用新的随机数字集更新TrackerKeys属性.我正在传回上一个列表,以确保用户不会再次看到相同的图像.

跟踪器键已正确设置并传递回视图.

我的问题是：

图像根据列表中的新值正确显示新图像

然而

隐藏字段的值不会更新为新值 – 它们保留原始值.

有任何想法吗？这是MVC3的错误吗？任何投入将不胜感激.谢谢.

编辑

提交前的HTML：

<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/26.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/33.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/8.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/30.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/6.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/18.gif" width="35" />  

和

<input id="TrackerKeys_0_" name="TrackerKeys[0]" type="hidden" value="26" />
<input id="TrackerKeys_1_" name="TrackerKeys[1]" type="hidden" value="33" />
<input id="TrackerKeys_2_" name="TrackerKeys[2]" type="hidden" value="8" />
<input id="TrackerKeys_3_" name="TrackerKeys[3]" type="hidden" value="30" />
<input id="TrackerKeys_4_" name="TrackerKeys[4]" type="hidden" value="6" />
<input id="TrackerKeys_5_" name="TrackerKeys[5]" type="hidden" value="18" />

之后：
在这里纠正新的价值……

<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/16.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/20.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/11.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/19.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/26.gif" width="35" />
<img alt="Security Character" height="35" src="http://localhost:51414/content/imagescss/15.gif" width="35" /> 

和…
仍保留旧价值……

<input id="TrackerKeys_0_" name="TrackerKeys[0]" type="hidden" value="26" />
<input id="TrackerKeys_1_" name="TrackerKeys[1]" type="hidden" value="33" />
<input id="TrackerKeys_2_" name="TrackerKeys[2]" type="hidden" value="8" />
<input id="TrackerKeys_3_" name="TrackerKeys[3]" type="hidden" value="30" />
<input id="TrackerKeys_4_" name="TrackerKeys[4]" type="hidden" value="6" />
<input id="TrackerKeys_5_" name="TrackerKeys[5]" type="hidden" value="18" />

控制器动作

[HttpPost]
    public ActionResult EmployerRegistration(EmployerViewModel Model)
    {
        if (ModelState.IsValid)
        {
            //do bits here
        }

        Model.TrackerKeys = Helper.GenerateNewNumbers(Model.TrackerKeys); 
        return View(Model);
    }

解决方法:

Is this a bug with MVC3?

哦,不,这是设计的,它是所有HTML助手在ASP.NET MVC中的工作方式. HTML帮助程序(例如Html.TextBoxFor,Html.HiddenFor,…)在绑定它们的值时首先查看ModelState,然后查看Model.因此,如果您打算在POST控制器操作中修改模型的某些属性,并且此属性是POST主体的一部分,则必须首先从ModelState中删除旧值：

[HttpPost]
public ActionResult EmployerRegistration(EmployerViewModel Model)
{
    if (ModelState.IsValid)
    {
        //do bits here
    }

    // we clear all values from the modelstate => this will ensure that
    // the helpers will use the values from the model and not those that
    // were part of the initial POST.
    ModelState.Clear();
    Model.TrackerKeys = Helper.GenerateNewNumbers(Model.TrackerKeys); 
    return View(Model);
}

或者如果您不想清除整个ModelState(因为这将删除可能与它们关联的所有值和任何相应的模型状态错误),您只能删除实际修改的那些键：

[HttpPost]
public ActionResult EmployerRegistration(EmployerViewModel Model)
{
    if (ModelState.IsValid)
    {
        //do bits here
    }

    for (var i = 0; i < Model.TrackerKeys.Count; i++)
    {
        ModelState.Remove(string.Format("TrackerKeys[{0}]", i));
    }
    Model.TrackerKeys = Helper.GenerateNewNumbers(Model.TrackerKeys); 
    return View(Model);
}