Question

这可能是我遇到的最令人沮丧的错误。

我有一个与广告位有很多关系的实体频道。在创建时，用户可以选择他们想要属于他们频道的广告位。

我有这个型号：

[Required]
[Display(Name = "Name")]
public string ChannelName { get; set; }

[Display(Name = "Description")]
public string ChannelDescription { get; set; }

//TODO: Add Sub Publisher Drop-Down

[Required(ErrorMessage = "You must select at least one Ad Slot.")]
[Display(Name = "Ad Slot(s)")]
public MultiSelectList AdSlots { get; set; }

这在我看来：

<div class="field">
    @Html.LabelFor(m => m.ChannelName)
    @Html.TextBoxFor(m => m.ChannelName)
    @Html.ValidationMessageFor(m => m.ChannelName)
</div>
<div class="field">
    @Html.LabelFor(m => m.ChannelDescription)
    @Html.TextAreaFor(m => m.ChannelDescription, new { @class = "description" })
    @Html.ValidationMessageFor(m => m.ChannelDescription)
</div>
<div class="field">
    @Html.LabelFor(m => m.AdSlots)
    @Html.ListBoxFor(m => m.AdSlots, new MultiSelectList(new[] { new { Value = "", Text = "" } }, "Value", "Text", new[] { "" }), new { Class = "multiselect", Multiple = "multiple", Size = 12 })
    @Html.ValidationMessageFor(m => m.AdSlots)
</div>

这是我处理处理的控制器操作：

//GET: /publishers/channels/new
public ActionResult New()
{
    return View();
}

//POST: /publishers/channels/new
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult New(Models.Channels.Create channelModel)
{
    if (ModelState.IsValid)
    {
        // Channel
        Core.Linq.APMaster.Channel channel = new Core.Linq.APMaster.Channel();
        channel.PublisherId = PublisherId;
        channel.Guid = Guid.NewGuid();
        channel.ChannelName = channelModel.ChannelName;
        channel.ChannelDescription = channelModel.ChannelDescription;
        channel.DateCreated = DateTime.UtcNow;
        channel.UserCreated = PublisherId;
        //TODO: Fix CreatedFromIP data-type bug.
        channel.CreatedFromIP = 0;
        channel.IsActive = true;
        channel.IsCustom = false;
        myDBContext.APMasterDBC.Channels.InsertOnSubmit(channel);

        // Ad Slots
        foreach (SelectListItem adSlotModel in channelModel.AdSlots)
        {
            Core.Linq.APMaster.ChannelAdSlot channelAdSlot = new Core.Linq.APMaster.ChannelAdSlot();
            channelAdSlot.ChannelId = channel.ChannelId;
            channelAdSlot.AdSlotId = int.Parse(adSlotModel.Value);
            channelAdSlot.IsActive = true;
            myDBContext.APMasterDBC.ChannelAdSlots.InsertOnSubmit(channelAdSlot);

        }

        myDBContext.APMasterDBC.SubmitChanges();

        TempData["flash"] = "Your Channel Has Been Created";

        return RedirectToAction("Index");
    }
    else
    {
        TempData["flash"] = "Your Channel Has Not Been Created";
    }

    return View(channelModel);
}

如您所见，我正在尝试从MultiSelectList插入许多广告位。但是我继续得到：没有为这个对象定义无参数构造函数。

有谁知道这是为什么？有人可以告诉我我做错了什么吗？为什么要扔这个？

Answer 1

我发现感谢这篇文章： Pass SelectList "SelectedValue" to Controller Action Method

模型类型必须简单（例如int []）然后我使用ViewData来填充列表。

没有为此对象定义的无参数构造函数。处理MultiSelectList时

1 个答案: