在DropDownListFor中绑定选定值用于语句中的-in

问题描述：

我有一个允许同时编辑多个地址项的视图。文本框的绑定工作正常，但下拉列表不能识别所选值。在DropDownListFor中绑定选定值用于语句中的-in

我的ViewModels是：

public class AddressesViewModel 
{ 
    public List<AddressViewModel> Addresses { get; set; } 
} 

public class AddressViewModel 
{ 
    public string Street { get; set; } 
    public string StateSelected { get; set; } 
    public IEnumerable<SelectListItem> States { get; set; } 

    public AddressViewModel() 
    { 
     this.States = new List<SelectListItem> { 
      new SelectListItem(), 
      new SelectListItem { Text = "New Jersey", Value = "NJ"}, 
      new SelectListItem { Text = "New York", Value = "NY"}, 
      new SelectListItem { Text = "Pennsylvania", Value = "PA" }, 
      new SelectListItem { Text = "Rhode Island", Value = "RI" } 
     }; 
    } 
}

我的控制器操作是：

public ActionResult Index() 
{ 
    var addressesViewModel = new AddressesViewModel(); 
    addressesViewModel.Addresses = new List<AddressViewModel>() { 
     new AddressViewModel{ 
      Street = "some road", 
      StateSelected = "PA" 
     }, 
     new AddressViewModel{ 
      Street = "some other road", 
      StateSelected = "NJ" 
     } 
    }; 

    return View(addressesViewModel); 
}

和我的观点是：

@model HelloWorld.Models.AddressesViewModel 


@for (int i = 0; i < Model.Addresses.Count(); i++) 
{ 
    <div class="editor-label"> 
     @Html.LabelFor(modelItem => Model.Addresses[i].Street) 
    </div> 
    <div class="editor-field"> 
     @Html.EditorFor(modelItem => Model.Addresses[i].Street) 
    </div> 

    <div class="editor-label"> 
     @Html.LabelFor(modelItem => Model.Addresses[i].StateSelected) 
    </div> 
    <div class="editor-field"> 
     @Html.DropDownListFor(modelItem => Model.Addresses[i].StateSelected, Model.Addresses[i].States) 
    </div> 
}

我测试使用单一项目视图（绑定到AddressViewModel），它工作正常。

发现了一些其他有同样的问题：http://stackoverflow.com/questions/8669470/the-selected-item-does-not-display-when-i-use-dropdownlist http://stackoverflow.com/questions/2631397/dropdownlistfor-does-not-select-value-if-in-for-loop http ：//stackoverflow.com/questions/17381635/dropdownlistfor-does-not-select-correct-value-in-a-loop – popdan 2014-08-29 13:37:22

答

随着从评论中的链接帮助下，我最终加入了每个到我的控制器：

public ActionResult Index() 
{ 
    var addressesViewModel = new AddressesViewModel(); 
    addressesViewModel.Addresses = new List<AddressViewModel>() { 
     new AddressViewModel{ 
      Street = "some road", 
      StateSelected = "PA" 
     }, 
     new AddressViewModel{ 
      Street = "some other road", 
      StateSelected = "NJ" 
     } 
    }; 

     foreach (var item in addressesViewModel.Addresses) 
     { 
      if (item.StateSelected != null) 
      { 
       item.States.First(x => x.Value == item.StateSelected).Selected = true; 
      } 
     } 

    return View(addressesViewModel); 
}

在DropDownListFor中绑定选定值用于语句中的-in

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