asp.net-mvc - 如何正确设置 SelectListItem 中的选定项目？

Question

我建立了一个新的 SelectListItem。我可以填充选项，但它不会让我设置所选项目：

模型值

Model.Clients.ClientId = 1
Model.Clients.Name = "Company 1"
Model.Clients.ClientId = 2
Model.Clients.Name = "Company 2"
Model.Clients.ClientId = 3
Model.Clients.Name = "Company 3"
Model.Clients.ClientId = 4
Model.Clients.Name = "Company 4"
Model.Clients.ClientId = 5
Model.Clients.Name = "Company 5"

Model.User.Client.ClientId = 3

DropDownListFor

@Html.DropDownListFor(model => model.User.Client, Model.Clients.Select(x => new SelectListItem
{
    Text = x.Name,
    Value = x.ClientId.ToString(),
    Selected = x.ClientId == Model.User.Client.ClientId
    }).ToList(),
    new { @class = "form-control" }
)

下拉列表 HTML

<select class="form-control" id="User_Client" name="User.Client">
    <option value="1">Company 1</option>
    <option value="2">Company 2</option>
    <option value="3">Company 3</option>
    <option value="4">Company 4</option>
    <option value="5">Company 5</option>
</select>

我的代码应该使选项 3 成为所选项目，但事实并非如此。

Answer 1

试试下面的代码：

@Html.DropDownListFor(model => model.User.Client.ClientId, 
new SelectList(Model.Clients,"ClientId","Name", Model.User.Client.ClientId), 
new { @class = "form-control" })

注意：不能Client为 DropDownList 绑定类，需要使用ClientId.

最好为选定的客户端添加另一个属性。如下所示：

public class yourModel
{
   public int selectedClientId {get;set;}
   //
}

    @Html.DropDownListFor(model => model.selectedClientId, 
    new SelectList(Model.Clients,"ClientId","Name", Model.User.Client.ClientId), 
    new { @class = "form-control" })

Answer 2

试试下面的

 @Html.DropDownListFor(model  => model.User.Client,
 new SelectList(Model.Clients.ToList(), "ClientId", "Name", Model.User.Client.ClientId))