blocks|key|1277871|text|我也得到了同样的结果。当使用foreach循环一个DropDownListFor+(即在一个页面上呈现多个选择元素)时。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1277872|我的变通方法是在控制器而不是视图中设置选定的值:类似于：|1277873|在控制器中：|1277874|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;+}++++++++
}|code-block|syntax|javascript|1277875|在视图中|1277876|<table>++++++++++++++++++++++++
+++<%25+for+(int+i=0;+i+<+Model.collectionOfFruitLists.Count;+i%2B%2B+)
++++++++{+%25>
++++++++<tr>++++++++++++++++++++++++++++
++++++++++++<td><%25:+Html.DropDownList("fruitSelectList",+collectionOfFruitLists[i].fruits,+"Please+select...")+%25></td>++++++++++++++++
++++++++</tr>
++++++++<%25}+%25>
+</table>|1277877|最妙的地方是控制器中的Selected+=+o.fruitID+==+selectedFruit，它的作用类似于SQL+CASE语句；Lance+Fisher对此进行了很好的解释(感谢兰斯，你的帖子真的帮了我的忙:)|offset|length|style|CODE|1277878|entityMap|0|LINK|mutability|MUTABLE|url|http://lancefisher.net/blog/archive/2008/05/07/linq-to-sql---case-statements.aspx#^0|0|0|0|0|0|0|B|11|1V|C|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|15|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|16|8|@]|9|@]|A|$]]|$1|M|3|N|5|H|7|17|8|@]|9|@]|A|$I|J]]|$1|O|3|P|5|6|7|18|8|@$Q|19|R|1A|S|T]]|9|@$Q|1B|R|1C|1|1D]]|A|$]]|$1|U|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]]]

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

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

In the controller:

<pre><code>public class FruitList 
{ 
 public int? selectedFruit{ get; set; }
 public List&lt;SelectListItem&gt; fruits
 {
 get
 {
 fruitEntities F = new fruitEntities();
 List&lt;SelectListItem&gt; 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&lt;FruitList&gt; collectionOfFruitLists { get; set; } 
}
</code></pre>

In the view

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

The nifty bit is <code>Selected = o.fruitID == selectedFruit</code> in the controller which acts like a SQL CASE statement; this is really well explained by <a href="http://lancefisher.net/blog/archive/2008/05/07/linq-to-sql---case-statements.aspx#">Lance Fisher</a> (thanks Lance, your post really helped me out :)

blocks|key|1277923|text|这是一个小技巧，依赖于JavaScript，但它对我来说工作得很好。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1277924|您需要知道这些字段将生成的客户端ID(通常可以手动计算出这些ID，但为了安全起见，您可能希望使用FieldIDFor+method之类的东西。|offset|length|1277925|您只需要在jQuery的$(.ready)文档中根据模型设置值：|1277926|<script+type="text/javascript">
++++$(document).ready(function+()+{
++++++++@for(var+i+=+0;+i+<+5;+i%2B%2B)
++++++++{
++++++++++++<text>
++++++++++++++++$("#@Html.FieldIDFor(m+=>+m.Countries[i])").val("@Model.Countries[i]");
++++++++++++</text>
++++++++}
++++});
</script>|code-block|syntax|javascript|1277927|entityMap|0|LINK|mutability|MUTABLE|url|http://www.dominicpettifer.co.uk/Blog/37/strongly-typed--label--elements-in-asp-net-mvc-2^0|0|1C|H|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@$D|W|E|X|1|Y]]|A|$]]|$1|F|3|G|5|6|7|Z|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|10|8|@]|9|@]|A|$K|L]]|$1|M|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

This is a bit of a hack, and JavaScript reliant but it worked very well for me.

You'll need to know the client IDs that will be produced by the fields (usually these can be worked out manually but for safety you may want to use something like a <a href="http://www.dominicpettifer.co.uk/Blog/37/strongly-typed--label--elements-in-asp-net-mvc-2" rel="nofollow">FieldIDFor method</a>.

You just need to set the values based on the model, in jQuery's $(document).ready:

<pre><code>&lt;script type="text/javascript"&gt;
 $(document).ready(function () {
 @for(var i = 0; i &lt; 5; i++)
 {
 &lt;text&gt;
 $("#@Html.FieldIDFor(m =&gt; m.Countries[i])").val("@Model.Countries[i]");
 &lt;/text&gt;
 }
 });
&lt;/script&gt;
</code></pre>

blocks|key|1277978|text|不确定这是mv4的新特性还是在以前的版本中存在。但是DropDownListFor包含了一个用于SelectList构造函数的附加参数。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1277979|SelectList(IEnumerable,+String,+String,+Object)|code-block|syntax|javascript|1277980|例如：|1277981|Html.DropDownListFor(+x+=>+x.Countries[+i+],+New+SelectList(Model.CountryList,"ID","Description",Model.Countries[i]))|1277982|其中ID是CountryList对象中的国家/地区ID，Description是国家/地区名称。|offset|length|style|CODE|1277983|entityMap^0|0|0|0|0|2|2|5|B|S|B|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@$M|X|N|Y|O|P]|$M|Z|N|10|O|P]|$M|11|N|12|O|P]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|13|8|@]|9|@]|A|$]]]|R|$]]

Not sure if this is new to mv4 or if it exists in prior version. But the DropDownListFor includes an additional parameter for the SelectList Constructor.

<pre><code>SelectList(IEnumerable, String, String, Object)
</code></pre>

For example:

<pre><code>Html.DropDownListFor( x =&gt; x.Countries[ i ], New SelectList(Model.CountryList,"ID","Description",Model.Countries[i]))
</code></pre>

Where <code>ID</code> is the Country ID in the <code>CountryList</code> object and <code>Description</code> is the Country Name.

blocks|key|1063404|text|我知道这个问题有点老了，但我只是在遍历对象列表并尝试将值绑定到我的编辑视图中的DropDownListFor时遇到了这个问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1063405|我用一个内联解决方案克服了这个问题，我使用了其他人为这个问题提供的一些以前解决方案中的逻辑。|1063406|绑定到我的模型：|1063407|@Html.DropDownListFor(model+=>+model.QuestionActions[i].QuestionActionTypeId,
++++++Model.QuestionActionTypes.Select(x+=>+new+SelectListItem()+{+Value+=+x.Value,+Text+=+x.Text,+Selected+=+(x.Value+==+Model.QuestionActions[i].QuestionActionTypeId.ToString())+}).ToList(),
++++++++++"Select+Action+Type",
+++++++++++++++++new+{+})|code-block|syntax|javascript|1063408|Model.QuestionActionTypes是一个填充在我的控制器中的SelectList。|1063409|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|R|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I know this question is a bit old but I just came across this problem with looping through a list of objects and attempting to bind the values to DropDownListFor(s) in my Edit View.

I overcame the issue with an inline solution by using the logic from some of the previous solutions given by others for this question.

Binding to my Model:

<pre><code>@Html.DropDownListFor(model =&gt; model.QuestionActions[i].QuestionActionTypeId,
 Model.QuestionActionTypes.Select(x =&gt; new SelectListItem() { Value = x.Value, Text = x.Text, Selected = (x.Value == Model.QuestionActions[i].QuestionActionTypeId.ToString()) }).ToList(),
 "Select Action Type",
 new { })
</code></pre>

Model.QuestionActionTypes is a SelectList that is populated in my Controller.

blocks|key|1063471|text|不要在视图模型中使用IEnumerable，而是使用如下所示的对象列表：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1063472|public+List<PairVM<string,string>>+TiposValorCobertura+{+get;+private+set;+}|code-block|syntax|javascript|1063473|在您的视图中，当您为循环中的dropdownlist分配可选元素时，请这样做：|1063474|@Html.DropDownListFor(m+=>+m.Coberturas[i].TipoLimiteInferior,+new+SelectList(Model.TiposValorCobertura,"Key","Description",++Model.Coberturas[i].TipoLimiteIferior))|1063475|其中"Key“和"Description”是PairVM的属性|1063476|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Instead of using a IEnumerable in your viewmodel use a List of objects like this one:

<pre><code>public List&lt;PairVM&lt;string,string&gt;&gt; TiposValorCobertura { get; private set; }
</code></pre>

And in your view when you assign the selectable elements for the dropdownlist in the loop, do it this way:

<pre><code>@Html.DropDownListFor(m =&gt; m.Coberturas[i].TipoLimiteInferior, new SelectList(Model.TiposValorCobertura,"Key","Description", Model.Coberturas[i].TipoLimiteIferior))
</code></pre>

Where "Key" and "Description" are PairVM's properties

In my view

<pre><code>&lt;%= Html.DropDownListFor( x =&gt; x.Countries[ i ], Model.CountryList )%&gt;
</code></pre>

in my controller

<pre><code>public int[ ] Countries { get; set; }

public List&lt;SelectListItem&gt; CountryList { get; set; }
</code></pre>

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.

DropDownListFor does not select value if in for loop

jQuery

在我看来<%= Html.DropDownListFor( x => x.Countries[ i ], Model.CountryList )%>在我的控制器中public int[ ] Countries { get; set; }public List<SelectListItem> CountryList { ...

问如果在for循环中，DropDownListFor不选择值
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