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我正在連接到實體框架的MVC應用程序。在我看來，我有一個下拉列表。代碼如下所示：MVC dropdownlist錯誤顯示
@{
ViewBag.Title = "ClassesPickGroup"; } @model ClassDeclarationsThsesis.Models.ClassesPickGroupViewModel
<h2>ClassesPickGroup</h2>
@foreach (var user in Model.users) {
if (user.email.Replace(" ", String.Empty) == HttpContext.Current.User.Identity.Name)
{
if (user.user_type.Replace(" ", String.Empty) == 3.ToString() || user.user_type.Replace(" ", String.Empty) == 2.ToString())
{
using (Html.BeginForm("ClassesPickGroup", "Account", FormMethod.Post, new { @class = "form-horizontal", role = "form" }))
{
@Html.AntiForgeryToken()
<h4>Generate summary views</h4>
<hr />
@Html.ValidationSummary("", new { @class = "text-danger" })
<div class="form-group">
@{
List<SelectListItem> listItems1 = new List<SelectListItem>();
foreach (var sub in Model.subjects)
{
if (sub.name.Replace(" ", String.Empty) == Model.subject_name.Replace(" ", String.Empty))
{
Model.subject_id = sub.class_id;
}
}
foreach (var group in Model.groups)
{
if (group.class_id == Model.subject_id)
{
listItems1.Add(new SelectListItem
{
Text = group.name,
Value = group.name,
});
}
}
}
@Html.LabelFor(m => m.selected_group, new { @class = "col-md-2 control-label" })
<div class="col-md-10">
@Html.DropDownListFor(m => m.selected_group, listItems1, new { @class = "form-control" })
</div>
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" class="btn btn-default" value="Submit" />
</div>
</div>
}
}
if (user.user_type.Replace(" ", String.Empty) == 1.ToString())
{
<p>You do not have enough permissions to enter this page. Contact the administrator.</p>
}
}
}
但是，在我的下拉列表中，我看到了錯誤的東西。元素的數量是正確的，但所有名稱都是相同的，所有名稱都對應於從模型中選擇的第一個匹配的「組」。我做錯了什麼？
我的控制器看起來是這樣的：
public ActionResult ClassesPickGroup(ClassesPickGroupViewModel value)
{
ClassDeclarationsDBEntities1 entities=new ClassDeclarationsDBEntities1();
int subj_id=0;
ClassesPickGroupViewModel model=new ClassesPickGroupViewModel();
model.subject_name = value.subject_name;
foreach (var subject in entities.Subjects)
{
if(subject.name.Replace(" ",String.Empty)==value.subject_name.Replace(" ", String.Empty))
{
subj_id = subject.class_id;
}
}
model.groups = entities.Groups.ToList();
model.subjects = entities.Subjects.ToList();
model.users = entities.Users.ToList();
if (ModelState.IsValid)
{
return RedirectToAction("ClassesView", "Account");
}
else
{
model.groups = entities.Groups.ToList();
model.subjects = entities.Subjects.ToList();
model.users = entities.Users.ToList();
return View(model);
}
return View(model);
}
顯然，添加組無法正常工作，集團不是唯一的（但在數據庫中他們是）。它有什麼問題？
是否'Model.groups'具有唯一的組？看起來你是下拉列表選項正在通過循環來構建。當你的if條件返回true時，你還要添加一個新的SelectListItem。它會只返回一次還是多於一次？這一切都取決於你在'Model.groups'中有什麼數據' – Shyju
@Shyju請參閱編輯 –
'class_id'屬性值是唯一的嗎？ 'Model.subject_id'的價值是什麼？ （貌似你試圖設置的該值在視圖中的代碼，你可以打印第二foreach循環之前，看看它是一個有效的值類標識碼？ – Shyju