Question

我很困惑如何让下拉列表显示所选的值。

型号：

public class SampleModel
{        
    public string State { get; set; }
}

控制器：

public ActionResult EditInformation()
{
    ViewBag.State = new SelectList(db.States, "StateName", "StateName");

    string userEmail = User.Identity.GetUserName();

    Sample model = new SampleModel();     
    model.State = "Melbourne";

    return View(model);
}

查看：

@Html.DropdownListFor(m => m.State, ViewBag.State as IEnumerable<SelectListItem>, "-- Select State --")

列表显示状态很好，但它没有自动选择我指定的值（＆＃34;墨尔本＆＃34;）。我已经尝试使用selectlist构造函数来分配selectedValue，但是在做了大量研究后，有人写道如果使用Html.DropdownListFor()则使用selectlist构造函数是多余的，因为你将使用分配给它的值。模型。

编辑：

这是我的db.State模型：

public class State
{
    [Key]
    public int StateId { get; set; }
    public string StateName { get; set; }

}

再次澄清一下，我想使用StateName作为值和selectlistitem的文本。

编辑：我的完整行动方法：

public ActionResult EditInformation()
    {
        //var states = ndb.States.Select(s => new SelectListItem { Text = s.StateName, Value = s.StateName , Selected = s.StateName == "Jawa Timur" }).ToList();

        ViewBag.State = new SelectList(ndb.States, "StateName", "StateName");
        ViewBag.City = new SelectList(ndb.Cities, "CityName", "CityName");
        string[] countries = { "Indonesia" };
        ViewBag.Country = new SelectList(countries);

        string userEmail = User.Identity.GetUserName();
        try
        {
            UserInformation userInfo = ndb.UserInformations.Single(m => m.Email == userEmail);
            UserAccountViewModel model = new UserAccountViewModel();

            model.Address = userInfo.Address;
            model.Email = userEmail;
            model.FirstName = userInfo.FirstName;
            model.LastName = userInfo.LastName;
            model.Phone = userInfo.Phone;
            model.PostalCode = userInfo.PostalCode;
            Debug.Print(userInfo.State);
            model.State = userInfo.State;
            model.City = userInfo.City;
            model.Country = userInfo.Country;


            return View(model);
        }catch { }
        return View();

    }

Answer 1

iron:router@1.0.12
iron:middleware-stack@1.0.11
underscore@1.0.6

在EditInformation View中，您需要有一个actionlink链接到用户的ID，以便您提取正确的信息，所以：

EditInformation View：

public ActionResult EditInformation(int? id /*this will be passed from your route values in your view*/)
{
    State myState = db.States.Find(id)


    ViewBag.State = new SelectList(ndb.States, "StateId", "StateName", myState.StateId);
}//I only added this because this is what the question pertains to.

Answer 2

试试这个：

public class SampleModel
{        
    public int Id { get; set; }
    public string State { get; set; }
}

控制器：

public ActionResult EditInformation()
{
    //Select default value like this (of course if your db.States have an Id):
    ViewBag.State = new SelectList(db.States, "Id", "StateName", 1 /*Default Value Id or Text*/);
    . . .
    return View();
}

SelectList(IEnumerable, String, String, Object) - 使用列表的指定项目，数据值字段，数据文本字段，和选定值初始化SelectList类的新实例。

查看：

@Html.DropdownList("State", null, "-- Select State --")

或者像你一样：

@Html.DropdownListFor(m => m.State, ViewBag.State as IEnumerable<SelectListItem>, "-- Select State --")

更新：

您可以使用jQuery获取Selected文本，如下所示：添加@Html.HiddenFor(x => x.State)

@Html.DropdownListFor(m => m.State, ViewBag.State as IEnumerable<SelectListItem>, "-- Select State --", new { id = "stateId" })
@Html.HiddenFor(x => x.State)

JS：

$(function () {
$("form").submit(function(){
    var selectedText= $("#stateId :selected").text();
    $("#State").val(selTypeText);           
  });
});

发表：

[HttpPost]
public void UploadDocument(State model)
{
   if(ModelState.IsValid)
   {
      string state = model.State;
   }
}

Answer 3

好的，所以经过一段时间的研究，问题在于命名惯例。显然，您无法将ViewBag.State用于Html.DropdownListFor(m => m.State)，这会导致Html.DropdownListFor(m => m.State)无法正确读取数据。

DropdownListFor不显示所选值

3 个答案: