Question

我试图在每个动作之前插入一个断点，当我在HttpGet方法中的ClassId值取得需要删除的类的实际（正确）Id而HttpPost方法中的ClassId值与之匹配时，我陷入了困境。 HttpGet方法的ClassId值，HttpPost中ClassId的实际值返回null，因为我遇到异常错误，该对象具有null值。如果有人能够承认我如何消除这个错误，那将是非常好的。谢谢。下面分别是控制器的代码和相应的视图。

控制器代码

 [HttpGet]
    public IActionResult Delete(int ClassId)
    {
        return View(db.Class.Include(x => x.Student).First(c => c.ClassId == ClassId));
    }


   [ActionName("Delete")]
    [HttpPost]
    public IActionResult DeletePost(int ClassId)
    {
        var r = db.Class.First(a => a.ClassId == ClassId);
        var student = r.StudentId.ToString();
        db.Remove(r);
        db.SaveChanges();
        return RedirectToAction("Details", "Student", new { id = student });
    }

查看代码

 @model DemoProject.Models.Class

 @{
   ViewData["Title"] = "Delete Class";
  }

   <h3>Are you sure you want to delete this?</h3>
                <div>
                    <hr />
                    <dl class="dl-horizontal">
                        <dt>
                            @Html.DisplayNameFor(model => model.ClassName)
                        </dt>
                        <dd>
                            @Html.DisplayFor(model => model.ClassName)
                        </dd>
                        <dt>
                            @Html.DisplayNameFor(model => model.Title)
                        </dt>
                        <dd>
                            @Html.DisplayFor(model => model.Title)
                        </dd>
                        <dt>
                            @Html.DisplayNameFor(model => model.Text)
                        </dt>
                        <dd>
                            @Html.DisplayFor(model => model.Text)
                        </dd>

                    </dl>

                    <form asp-action="Delete">
                        <div class="form-actions no-color">
                            <input type="submit" value="Delete" class="btn btn-danger" /> 
                           <div class="row">
                               <a asp-action="Details" asp-controller="Student" asp-route-id="@Model.Student.StudentId">Back</a>
                           </div>
                        </div>
                    </form>
                </div>

Answer 1

您有两种选择：

正如@ stephen.vakil所说，在ClassId元素中为<form>属性添加隐藏字段。

使用隐藏字段查看

@model ModelBinding.Models.Class

@{
    ViewData["Title"] = "Delete Class";
}

<h3>Are you sure you want to delete this?</h3>
<div>
  <hr/>
  <dl class="dl-horizontal">
    <dt>
      @Html.DisplayNameFor(model => model.ClassName)
    </dt>
    <dd>
      @Html.DisplayFor(model => model.ClassName)
    </dd>
    <dt>
      @Html.DisplayNameFor(model => model.Title)
    </dt>
    <dd>
      @Html.DisplayFor(model => model.Title)
    </dd>
    <dt>
      @Html.DisplayNameFor(model => model.Text)
    </dt>
    <dd>
      @Html.DisplayFor(model => model.Text)
    </dd>

  </dl>

  <form asp-action="Delete">
    <div class="form-actions no-color">
      @Html.HiddenFor(model => model.ClassId)
      <input type="submit" value="Delete" class="btn btn-danger"/>
      <div class="row">
        <a asp-action="Details" asp-controller="Student" asp-route-id="@Model.Student.StudentId">Back</a>
      </div>
    </div>
  </form>
</div>

将asp-route-id="@Model.ClassId"添加到您的<form>代码，并将ClassId方法的DeletePost参数名称更改为id。

使用asp-route-id查看

@model ModelBinding.Models.Class

@{
    ViewData["Title"] = "Delete Class";
}

<h3>Are you sure you want to delete this?</h3>
<div>
  <hr/>
  <dl class="dl-horizontal">
    <dt>
      @Html.DisplayNameFor(model => model.ClassName)
    </dt>
    <dd>
      @Html.DisplayFor(model => model.ClassName)
    </dd>
    <dt>
      @Html.DisplayNameFor(model => model.Title)
    </dt>
    <dd>
      @Html.DisplayFor(model => model.Title)
    </dd>
    <dt>
      @Html.DisplayNameFor(model => model.Text)
    </dt>
    <dd>
      @Html.DisplayFor(model => model.Text)
    </dd>

  </dl>

  <form asp-action="Delete" asp-route-id="@Model.ClassId">
    <div class="form-actions no-color">
      <input type="submit" value="Delete" class="btn btn-danger"/>
      <div class="row">
        <a asp-action="Details" asp-controller="Student" asp-route-id="@Model.Student.StudentId">Back</a>
      </div>
    </div>
  </form>
</div>

具有重命名的操作参数的控制器

[HttpGet]
public IActionResult Delete(int classId)
{
    return View(db.Class.Include(x => x.Student).First(c => c.ClassId == classId));
}

[ActionName("Delete")]
[HttpPost]
public IActionResult DeletePost(int id)
{
    var r = db.Class.First(a => a.ClassId == id);
    var student = r.StudentId.ToString();
    db.Remove(r);
    db.SaveChanges();
    return RedirectToAction("Details", "Student", new { id = student });
}

除非您出于某种原因无法使用<hidden>字段，否则选项1是最佳选择。

控制器中的HttpPost方法不与HttpGet方法

1 个答案: