ASP.NET MVC：DropDownListFor不选择任何选项 [英] ASP.NET MVC: DropDownListFor doesn't select any option

问题描述

我有这样的填充一个下拉在ASP.NET MVC视图列表

I have this to populate a drop down list in an ASP.NET MVC view.

<%= Html.DropDownListFor(model => model.Bikes,
      Model.Bikes.Select(
      x => new SelectListItem {
               Text = x.Name,
               Value = Url.Action("Details", "Bike", new { bikeId = x.ID }),
               Selected = x.ID == Model.ID,
           })) %>

调试这个我可以看到选属性设置为真正当它应该是。但是，当视图显示，没有在列表中的选项被选择。我意识到，这可能是与 DropDownListFor 的另一个重载做，但我真的很想得到这个版本的工作。

Debugging this I can see that the Selected property is set to true when it should be. But when the view is rendered, none of the options in the list is selected. I realize that this could be done with another overload of DropDownListFor but I really want to get this version working.

任何想法？

推荐答案

<击>您选择的价值不工作的原因是因为你使用URL作为选项值，但指定 Model.ID 的选子句。

尝试是这样的：

<%= Html.DropDownListFor(
    model => model.Bikes,
    new SelectList(Model.Bikes, "Id", "Name", Model.ID)
)%>

ID表示的属性，将作为期权的价值，而名称表示将用作选项标签的属性。

"Id" indicates the property that will be used as option value while "Name" indicates the property that will be used as option label.

如果您要保留 Url.Action 你可以尝试：

If you want to preserve the Url.Action you could try:

<%= Html.DropDownListFor(
    model => model.Bikes,
    new SelectList(Model.Bikes.Select(x => new {
        Id = x.Id,
        Name = Url.Action("Details", "Bike", new { bikeId = x.ID })
    }), "Id", "Name", Model.ID)
)%>

您会发现，我倒名称和ID，因为它似乎更符合逻辑使用模型ID作为选项值。

You will notice that I've inverted the Name and Id as it seemed more logical to use the model Id as option value.

更新：

这不工作的原因是因为你绑定到的IEnumerable （即 DropDownListFor 助手的第一个参数）。当您使用的是相同 model.Bikes 收藏这应该是一个标量属性：

The reason this doesn't work is because you are binding to an IEnumerable (the first argument of the DropDownListFor helper). It should be a scalar property while you are using the same model.Bikes collection:

<%= Html.DropDownListFor(
    model => model.SelectedBikeValue,
    Model.Bikes.Select(
        x => new SelectListItem {
                 Text = x.Name,
                 Value = Url.Action("Details", "Bike", new { bikeId = x.ID }),
                 Selected = x.ID == Model.ID,
        }
)) %>

我的话作为有关选项值代表真正不使用的URL。

My remark about not using Urls as option values stands true.

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