DropDownListFor未从模型中预先选择值

本文关键字：选择 模型 DropDownListFor | 更新日期: 2023-09-27 17:59:42

控制器代码：

AccountsDetailsViewModel vOwnerVM = Mapper.Map<VehicleOwner, AccountsDetailsViewModel>(vOwner);
AccountsDetailsAccountViewModel vOwnerDetailsVM = Mapper.Map<VehicleOwner, AccountsDetailsAccountViewModel>(vOwner);
ViewBag.FleetType = new SelectList(VehicleOwnerFleetTypeFactory.GetTypes().OrderBy(l => l.Type), "Id", "Type");
vOwnerVM.AccountDetails = vOwnerDetailsVM;

主视图型号代码：

public class AccountsDetailsViewModel
{
    public AccountsDetailsAccountViewModel AccountDetails { get; set; }
}

主视图代码

@model X.Views.Accounts.ViewModels.AccountsDetailsViewModel
@Html.Partial("DetailsAccount", @Model.AccountDetails)

部分视图模型代码：

[DisplayName("Fleet Type")]
public int FleetType { get; set; }

部分视图代码

@model X.Views.Accounts.ViewModels.AccountsDetailsAccountViewModel
@Html.DropDownListFor(model => model.FleetType, 
    (IEnumerable<SelectListItem>)ViewBag.FleetType)
@Html.DisplayFor(model => model.FleetType) (FOR DEBUG)

车辆所有者FleetType类

public class VehicleOwnerFleetType
{
    public int Id { get; set; }
    public string Type { get; set; }
}
public class VehicleOwnerFleetTypeFactory
{
    static readonly VehicleOwnerFleetType[] Types = new VehicleOwnerFleetType[] {
            new VehicleOwnerFleetType() {Id = 0, Type = "Unknown"},
            new VehicleOwnerFleetType() {Id = 1, Type = "HGV"},
            new VehicleOwnerFleetType() {Id = 2, Type = "Car"},
            new VehicleOwnerFleetType() {Id = 3, Type = "Van"},
            new VehicleOwnerFleetType() {Id = 4, Type = "Mixed"}
        };
    public static VehicleOwnerFleetType[] GetTypes()
    {
        return Types;
    }
    public static VehicleOwnerFleetType GetType(int id)
    {
        return Types.FirstOrDefault(m => m.Id == id);
    }
}

无论数据库显示什么，下拉列表都不会显示模型中的正确值，只显示列表中的顶部值。

但是，如果我选择了一个值，然后提交表单以将更改保存到数据库，那么它确实提交了正确的值。

当在控制器中返回视图模型的视图时，这些值正好反映了数据库，我不明白它为什么要这样做。

编辑："扇区"下拉列表是唯一一个自动选择正确值的下拉列表。

DropDownListFor未从模型中预先选择值

问题可能是由于您的selectlist和VM的成员变量具有相同的名称。

model.FleetType

和

(IEnumerable<SelectListItem>)ViewBag.FleetType

尝试将选择列表重命名为FleetTypeList或类似

对我来说很好。检查是否将模型传递给视图。

@using WebApplication2.Controllers
@model WebApplication2.Controllers.MyModel
@{
    ViewBag.Title = "Home Page";
    ViewBag.FleetType = new SelectList(
        VehicleOwnerFleetTypeFactory.GetTypes().OrderBy(l => l.Type),
        "Id", 
        "Type");
}
<div>
    <h2>---------------------------</h2>
    @Html.DropDownListFor(model => model.FleetType,
            (SelectList)ViewBag.FleetType)
    <h2>---------------------------</h2>
</div>

和

using System.Web.Mvc;
namespace WebApplication2.Controllers
{
    public class HomeController : Controller
    {
        public ActionResult Index()
        {
            return View(new MyModel { FleetType = 2 });
        }
    }
    public class MyModel
    {
        public int FleetType { get; set; }
    }
    public class VehicleOwnerFleetTypeFactory
    {
        public static FleetType[] GetTypes()
        {
            return new[]
                {
                    new FleetType {Id = 1, Type = "Type 1"},
                    new FleetType {Id = 2, Type = "Type 2"},
                    new FleetType {Id = 3, Type = "Type 3"}
                };
        }
    }
    public class FleetType
    {
        public int Id { get; set; }
        public string Type { get; set; }
    }
}
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