Question

我正在将ViewModel的值放入表单字段的视图中。在我的一个DropDownList中，值是正确的，但在另一个中，该值会重复自身而不是更改。我在做什么错了？

ViewModel：

namespace FulfillmentPortal.ViewModels
{
public class ViewModel
{
    [Required(ErrorMessage = "Please select a carrier")]
    public List<Carrier> CarrierList { get; set; }

    [Required(ErrorMessage = "Please select a service")]
    public List<CarrierService> ServiceList { get; set; }
}
}

控制器：

public class FulfillmentController : Controller
{
    private CarrierModel db = new CarrierModel();

    // GET: Fulfillment
    public ActionResult Index()
    {
        ViewModel vm = new ViewModel
        {
            CarrierList = db.Carriers.ToList(),
            ServiceList = db.CarrierServices.ToList()
        };
        return View(vm);
    }
}

查看：

@model FulfillmentPortal.ViewModels.ViewModel

@{
    ViewBag.Title = "index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}
<div class="panel panel-primary">
<div class="panel-heading">REPORT OPTIONS</div>
<div class="panel-body" style="padding-left:35px;">
    <form id="processForm" class="form-horizontal" action="~/Fulfillment/Report" method="post" enctype="multipart/form-data">
        <div class="form-group">
            <label for="sel1">Carrier:</label>
            @Html.DropDownListFor(model => model.CarrierList, new SelectList(Model.CarrierList, "CarrierId", "CarrierName"), "Select a Carrier",
                new { @class = "form-control", @style = "width:auto; margin-bottom:15px;" })
            <label for="sel2">Carrier Services:</label>
            @Html.DropDownListFor(model => model.ServiceList, new SelectList(Model.ServiceList, "Code", "WebName"), "Select a Service", 
                new { @class = "form-control", @style = "width:auto; margin-bottom:15px;" })           
        </div>
    </form>
</div>
</div>

型号：

public partial class CarrierModel : DbContext
    {
        public CarrierModel()
            : base("name=CarrierModel")
        {
        }

        public virtual DbSet<Carrier> Carriers { get; set; }

        public virtual DbSet<CarrierService> CarrierServices { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
        }
    }

 [HttpPost]
  public ActionResult Index(ViewModel viewModel)
  {
     if (ModelState.IsValid)
     {
         viewModel.CarrierList.ToList();
         viewModel.ServiceList.ToList();
     }

       return View(viewModel);
}

这是我的控制器。现在我的观点是错误的。我想我缺少了一些东西或误解了一些东西。请帮助我了解我所缺少的。

任何帮助都会很棒。谢谢！

Answer 1

DropDownListFor(model => model.ServiceList

这不是应该使用这种方法的方式，我怀疑这是您问题的答案。

该lambda应该提供一个字段，该字段将保留此下拉列表输出的值。对于您的情况，您应该在模型中有两个字段：

public class ViewModel
...
    public int CarrierId { get; set; }
    public string CarrierServiceCode { get; set; }

这些将保留当前选择的值，如果未选择（尚未），则不保存任何值。并且应该在该lambda中使用它们：

DropDownListFor(model => model.CarrierServiceCode

或者，您可以使用DropDownList()方法，该方法不需要模型中的字段，并为其指定一个自定义名称，该名称将随选定的值一起发布。

Answer 2

您的ViewModel应该如下：

public class ViewModel
{
    [Required(ErrorMessage = "Please select a carrier")]
    public int CarrierId {get; set;}

    [Required(ErrorMessage = "Please select a service")]
    public int ServiceCode {get; set;}


    public List<Carrier> CarrierList { get; set; }
    public List<CarrierService> ServiceList { get; set; }
}

然后在视图中：

<label for="sel1">Carrier:</label>
@Html.DropDownListFor(model => model.CarrierId, new SelectList(Model.CarrierList, "CarrierId", "CarrierName"), "Select a Carrier",
                new { @class = "form-control", @style = "width:auto; margin-bottom:15px;" })
<label for="sel2">Carrier Services:</label>
@Html.DropDownListFor(model => model.ServiceCode, new SelectList(Model.ServiceList, "Code", "WebName"), "Select a Service", 
                new { @class = "form-control", @style = "width:auto; margin-bottom:15px;" })

然后，您的Index Post方法应如下：

[HttpPost]
public ActionResult Index(ViewModel viewModel)
{
    if(ModelState.IsValid)
    {
       // do whatever you want with `viewModel.CarrierId` and `viewModel.ServiceCode` here
    }

    viewModel.CarrierList = db.Carriers.ToList();
    viewModel.ServiceList = db.CarrierServices.ToList();
    return View(viewModel);
}

为什么我的DropDownList重复相同的值？

2 个答案: