Question

大家好日子。我有下一个问题。

我有一个Edit窗体，上面有几个DropDownList控件。我需要根据我在db中的数据绑定DropDownListFor中的选定值。

我的下一步是：

型号：

供应商

public class Supplier{
    public int SupplierID { get; set; }       
    public string CompanyName { get; set; }
}

Delviery

public class Delivery{
    public int DeliveryID { get; set; }
    public string DeliveryCode { get; set; }
    public int SupplierID { get; set; }
    public virtual Supplier Supplier { get; set; }        
}

ViewModel for Delivery Edit屏幕：

public class DeliveryEditViewModel{
    public int DeliveryID { get; set; }        
    public string SelectedCompanyName { get; set; }
    public IEnumerable<SelectListItem> Suppliers { get; set; }
}

查看：

<dd>
    @Html.DropDownListFor(x => x.SelectedCompanyName, new SelectList(Model.Suppliers, "Value", "Text"), htmlAttributes: new { @class = "form-control" })
</dd>

控制器：

 // GET: Deliveries/Edit
public ActionResult Edit(int? id){   
    db.Configuration.ProxyCreationEnabled = false;
        DeliveryEditViewModel model = db.Deliveries.Include(s => s.Supplier).Include(a => a.Auction).Include(q => q.Quality).Include(t => t.BulbType)
                .Where(d => d.DeliveryID == id)
                .Select(x => new DeliveryEditViewModel{
                    DeliveryID = x.DeliveryID,
                    SelectedCompanyName = x.Supplier.CompanyName
                })
                .Single();               
    model.Suppliers = db.Suppliers.Where(s => s.IsActive == true).Select(x => new SelectListItem{
        Value = x.SupplierID.ToString(),
        Text = x.CompanyName
    });
    return View(model);
}

问题是我无法根据我在数据库中已有的数据在DropDownListFor中设置选定的值。相反，我总是使用DropDown控件，第一个元素处于活动状态。我已经从Html.DropdownListFor selected value not being set尝试过solutoin，但我仍然选择了第一个值，而不是真正的值。

研究时间和已经大胆的头发让我停下来寻求帮助。请帮我弄清楚它是如何可能的。

非常感谢你。

Answer 1

Suppliers已经IEnumerable<SelectListItem>为什么世界上你在视图中使用new SelectList(Model.Suppliers, "Value", "Text")创建另一个相同的？您需要设置SelectedCompanyName的值以匹配其中一个选项（即您的Suppliers表中SupplierID的值之一（但您的代码建议该属性应为int而不是{ {1}}）@StephenMuecke

Answer 2

正如我所建议你不要在控制器级别创建SelectListItems。你能做的是：

public class DeliveryEditViewModel
{
    public int DeliveryID { get; set; }        
    public string SelectedCompanyName { get; set; }
    public IEnumerable<Supplier> suppliers { get; set; }
}

控制器：

 // GET: Deliveries/Edit
public ActionResult Edit(int? id){   
    db.Configuration.ProxyCreationEnabled = false;
        DeliveryEditViewModel model = db.Deliveries.Include(s => s.Supplier).Include(a => a.Auction).Include(q => q.Quality).Include(t => t.BulbType)
                .Where(d => d.DeliveryID == id)
                .Select(x => new DeliveryEditViewModel{
                    DeliveryID = x.DeliveryID,
                    SelectedCompanyName = x.Supplier.CompanyName
                })
                .Single();               
    Model.suppliers = db.Suppliers.Where(s => s.IsActive == true);
    return View(model);
}

查看：

  @Html.DropDownListFor(model => model.SelectedCompanyName, ((IEnumerable<Supplier>)Model.supplierss).Select(x => new SelectListItem()
           {
               Text = x.CompanyName.ToString(),
               Value = x.SupplierID.ToString(),
               Selected = (Model != null) && (x.CompanyName == Model.SelectedCompanyName)
           }), "-- Select Supplier --")

这是一个非常有用的技巧，您可以更改文本或值或选定值或默认选定选项，而无需更改控制器并再次构建它以反映。

DropDownListFor基于数据库中的值选择值

2 个答案: