如果在循环DropDownListFor没有选择价值 [英] DropDownListFor does not select value if in for loop

问题描述

在我看来

<%= Html.DropDownListFor( x => x.Countries[ i ], Model.CountryList )%>

在我的控制器

public int[ ] Countries { get; set; }

public List<SelectListItem> CountryList { get; set; }

在形式被公布是没有问题的，下拉填充的值和用户选择的发布。但是，当我尝试用已赋值加载形式向国家[]它不会选择的。

When the forms gets posted there is no problem, the dropdown is populated and the values the user selects are posted. But when I try to load the form with already assigned values to the Countries[ ] it does not get selected.

推荐答案

我得到相同的了。当使用的foreach循环围绕DropDownListFor（即呈现一个页面上的多个选择元素）。

I'm getting the same too. When using foreach to loop around a DropDownListFor (i.e. to render multiple select elements on a page).

我的解决办法是在控制器而不是视图，设置所选值：是这样的：

My work around is to set the selected value in the controller rather than the view: something like this:

在控制器：

public class FruitList 
{        
    public int? selectedFruit{ get; set; }
    public List<SelectListItem> fruits
    {
        get
        {
            fruitEntities F = new fruitEntities();
            List<SelectListItem> list = (from o in F.Options
                                         select new SelectListItem
                                         {
                                             Value = o.fruitID,
                                             Text = o.fruit,                                                 
                                             Selected = o.fruitID == selectedFruit
                                         }).ToList();
            return list;
        }
    }
}

public class ViewModel 
{              
    public List<FruitList> collectionOfFruitLists { get; set; }        
}

在视图

<table>                        
   <% for (int i=0; i < Model.collectionOfFruitLists.Count; i++ )
        { %>
        <tr>                            
            <td><%: Html.DropDownList("fruitSelectList", collectionOfFruitLists[i].fruits, "Please select...") %></td>                
        </tr>
        <%} %>
 </table>

的漂亮位选择= o.fruitID == selectedFruit 中，就像一个SQL CASE语句的控制器;这实在是深受兰斯费舍尔（感谢兰斯，你真的后帮我了：）

The nifty bit is Selected = o.fruitID == selectedFruit in the controller which acts like a SQL CASE statement; this is really well explained by Lance Fisher (thanks Lance, your post really helped me out :)

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