C# Net Mvc选择器选择器

我正在尝试在我的应用程序中使用Bootstrap Selectpicker实现DropDownList Multi-Select来选择学校

我不太熟悉MVC和JQuery，因为我已经使用webforms很长一段时间了，所以我正在从internet学习来完成

以下是场景：

在我的布局中，有一个下拉列表：

@*DropDownList Select School*@                                            
@Html.DropDownList("Schools", null, null, new { id = "MultiSelect", @class = "selectpicker form-control", multiple = "", title = "School" })

public ActionResult Class()
{
    IEnumerable<SelectListItem> ListClasses = db.scasy_class
        .OrderBy(a => a.class_name)
        .Select(c => new SelectListItem
        {
            Value = c.id.ToString(),
            Text = c.class_name,
            Selected = false
        });
    ViewBag.Class = ListClasses.ToList();

    ClassViewModel classViewModel = new ClassViewModel()
    {
        SelectOptions = ListClasses
    };

    return View(classViewModel);
}

填写下拉列表的代码：

@*DropDownList Select School*@                                            
@Html.DropDownList("Schools", null, null, new { id = "MultiSelect", @class = "selectpicker form-control", multiple = "", title = "School" })

public ActionResult Class()
{
    IEnumerable<SelectListItem> ListClasses = db.scasy_class
        .OrderBy(a => a.class_name)
        .Select(c => new SelectListItem
        {
            Value = c.id.ToString(),
            Text = c.class_name,
            Selected = false
        });
    ViewBag.Class = ListClasses.ToList();

    ClassViewModel classViewModel = new ClassViewModel()
    {
        SelectOptions = ListClasses
    };

    return View(classViewModel);
}

以及控制器

public ActionResult SetSchool(int school, bool selected)
{
    ArrayList school_nos = Session["Schools"] as ArrayList;

    if (selected)
    {
        if (!school_nos.Contains(school))
        {
            school_nos.Add(school);
        }
    }
    else
    {
        if (school_nos.Contains(school))
        {
            school_nos.Remove(school);
        }
    }

    Session["Schools"] = school_nos;

    return new HttpStatusCodeResult(HttpStatusCode.OK);
}

public JsonResult GetSchool()
{
    IEnumerable<SelectListItem> ListSchools = db.scasy_school
        .OrderBy(a => a.name)
        .Select(a => new SelectListItem { Value = a.id.ToString(), Text = a.name});

    ArrayList school_nos = Session["Schools"] as ArrayList;

    List<SelectListItem> ListSchoolsUpdated = new List<SelectListItem>();

    foreach (var item in ListSchools)
    {
        SelectListItem selListItem;

        if (school_nos.Contains(item.Value.ToString()))
        {
            selListItem = new SelectListItem() { Value = item.Value.ToString(), Text = item.Text, Selected = true };
        }
        else
        {
            selListItem = new SelectListItem() { Value = item.Value.ToString(), Text = item.Text, Selected = false };
        }

        ListSchoolsUpdated.Add(selListItem);
    }
    return Json(ListSchoolsUpdated, JsonRequestBehavior.AllowGet);
}

在这里之前，它一直在按预期工作。 对于下一次重新加载，我尝试用相同的数据填充dropdownlist，但使用会话值用勾号显示以前选择的学校，因为我需要在许多其他页面上显示这些信息

$(document).ready(function () {
    $.getJSON("/Setup/Student/GetSchool/",
        function (data) {                     
            var myData = [];
            $.each(data, function (index, item) {
                if (item.Selected == true) {
                    myData.push(item.Value);
                }
            });
            //alert(myData);
            $('#MultiSelect').selectpicker('val', myData);                      
        });
});

以及控制器

public ActionResult SetSchool(int school, bool selected)
{
    ArrayList school_nos = Session["Schools"] as ArrayList;

    if (selected)
    {
        if (!school_nos.Contains(school))
        {
            school_nos.Add(school);
        }
    }
    else
    {
        if (school_nos.Contains(school))
        {
            school_nos.Remove(school);
        }
    }

    Session["Schools"] = school_nos;

    return new HttpStatusCodeResult(HttpStatusCode.OK);
}

public JsonResult GetSchool()
{
    IEnumerable<SelectListItem> ListSchools = db.scasy_school
        .OrderBy(a => a.name)
        .Select(a => new SelectListItem { Value = a.id.ToString(), Text = a.name});

    ArrayList school_nos = Session["Schools"] as ArrayList;

    List<SelectListItem> ListSchoolsUpdated = new List<SelectListItem>();

    foreach (var item in ListSchools)
    {
        SelectListItem selListItem;

        if (school_nos.Contains(item.Value.ToString()))
        {
            selListItem = new SelectListItem() { Value = item.Value.ToString(), Text = item.Text, Selected = true };
        }
        else
        {
            selListItem = new SelectListItem() { Value = item.Value.ToString(), Text = item.Text, Selected = false };
        }

        ListSchoolsUpdated.Add(selListItem);
    }
    return Json(ListSchoolsUpdated, JsonRequestBehavior.AllowGet);
}

public JsonResult GetSchool（）
{
IEnumerable ListSchools=db.scasy_学校
.OrderBy（a=>a.name）
.Select（a=>newselectListItem{Value=a.id.ToString（），Text=a.name}）；
ArrayList school_nos=作为ArrayList的会话[“学校”]；
List ListSchoolsUpdated=新列表（）；
foreach（列表学校中的var项目）
{
选择ListItem selListItem；
if（学校编号包含（item.Value.ToString（））
{
selListItem=new SelectListItem（）{Value=item.Value.ToString（），Text=item.Text，Selected=true}；
}
其他的
{
selListItem=new SelectListItem（）{Value=item.Value.ToString（），Text=item.Text，Selected=false}；
}
ListSchoolsUpdated.Add（selListItem）；
}
返回Json（ListSchoolsUpdated，JsonRequestBehavior.AllowGet）；
}

代码不会抛出错误，但我无法显示包含所选项目的dropdownlist

---

为页面声明一个模型类

public class ClassViewModel {
  public List<int> SelectedSchools {get; set;}
  public List<SelectListItem> Schools {get; set;}
}

然后在您的视图中，使用此代码显示dropdownlist

 @Html.ListBoxFor(m=> m.SelectedSchools , Model.Schools, new {id = "MultiSelect", @class = "selectpicker form-control", title = "School" })

---

感谢您的评论，DropDownList位于_Layout.cshtml上。