一次更新在asp.net的MVC多个记录 [英] Update multiple records at once in asp.net mvc

问题描述

我试图用使一个网站 asp.net mvc的4 ＆安培; EF6 ，我想所有的一次更新多行。但由于某些原因，它不工作和放大器;我得到了如下的错误，

I'm trying to make a website using asp.net mvc 4 & EF6 where I want to update multiple rows all at once. But for some reason, it's not working & I get an error like this,

System.NullReferenceException：对象不设置到对象的实例

System.NullReferenceException: Object reference not set to an instance of an object

下面是我的codeS，

Here are my codes,

控制器

[HttpPost]
    public ActionResult MakeDue(List<BillCheck> BillLists)
    {
        if (Session["username"] != null)
        {
            if (ModelState.IsValid)
            {
                foreach (var BillId in BillLists)
                {
                    var getDue = db.BillChecks.Where(p => p.id == BillId.id).FirstOrDefault();
                    getDue.due = BillId.due;
                }
                db.SaveChanges();
                return RedirectToAction("Success");
            }
            else
            {
                return RedirectToAction("Failed");
            }
        }
        else
        {
            return RedirectToAction("Login");
        }
    }

查看

@using (Html.BeginForm("MakeDue", "Home"))
{
    @Html.ValidationSummary(true)
    @foreach(var item in Model.DueList)
    {
        @Html.HiddenFor(modelItem => item.id)
        <tr>
            <td>@Html.DisplayFor(modelItem => item.flat)</td>
            <td>@Html.DisplayFor(modelItem => item.name)</td>
            <td>@Html.TextBoxFor(modelItem => item.due)</td>
        </tr>
    }
    <input type="submit" class="btn btn-success" value="Update" />
}

这是一个错误在我的code？我如何更新由于一次给所有的投入？

推荐答案

您第一个问题是您使用的foreach 循环正在产生重复的名称属性，不会绑定到一个集合，因此在 BillLists 参数将始终是一个空集（它也产生重复的 ID 属性是无效的HTML）。你需要使用一个为循环或自定义的 EditorTemplate 为typeof运算 BillCheck 。使用为循环，你的观点必须

Your first problem is that you use of a foreach loop is generating duplicate name attributes which will not bind to a collection and as a result the BillLists parameter will always be an empty collection (its also generating duplicate id attributes which is invalid html). You need to use a for loop or a custom EditorTemplate for typeof BillCheck. Using a for loop, your view need to be

using (Html.BeginForm("MakeDue", "Home"))
{
  @Html.ValidationSummary(true)
  @for(int i = 0; i < Model.DueList.Count; i++)
  {

    <tr>
      <td>
        @Html.HiddenFor(m => m.DueList[i].id)
        @Html.DisplayFor(m => m.DueList[i].flat)</td>
      <td>@Html.DisplayFor(m => m.DueList[i].name)</td>
      <td>@Html.TextBoxFor(m => m.DueList[i].due)</td>
    </tr>
  }
  <input type="submit" class="btn btn-success" value="Update" />
}

还要注意的是 @ Html.HiddenFor（）助手需要一个＆LT内部; TD＆GT; 元素为了有效的HTML。

Note also that the @Html.HiddenFor() helper need to be inside a <td> element in order to be valid html.

接下来的问题是，在视图模型不是typeof运算列表＆LT; BillCheck＆GT; ，但它确实包含一个名为属性决斗这是typeof运算列表＆LT; BillCheck＆GT; 让你的POST方法必须是

The next problem is that the model in the view is not typeof List<BillCheck>, but it does contain a property named DueList which is typeof List<BillCheck> so your POST method needs to be

public ActionResult MakeDue(YourModel model)

其中， YourModel 是您用于生成视图（类名，即在 @model ??? 声明）。然后你在回路控制器的方法必须是

where YourModel is the class name you used to generate the view (i.e. in the @model ??? statement). Then you loop in the controller method need to be

foreach (var BillId in model.DueList)
{
  var getDue = db.BillChecks.Where(p => p.id == BillId.id).FirstOrDefault();
  if (getDue != null) // add this
  {
    getDue.due = BillId.due;
  }
}
db.SaveChanges();

请注意还增设的如果（getDue！= NULL）检查

旁注：你正在检查如果（ModelState.IsValid）。建议您在返回的观点是的ModelState 是无效的，这样用户可以纠正错误。

Side note: Your are checking if (ModelState.IsValid). It is recommended you return the view is ModelState is not valid so that the user can correct any errors.

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