以下是相关代码.记住你,我在记事本中做了这个,而不是在我的代码中复制我的项目在工作.如果我拼错了一个类名,假设我的代码中没有拼写错误.没有编译错误.
模型：
public class Myviewmodel { public int SelectedSomething { get; set; } public IList<int> Somethings { get; set; } }
控制器：
public class MyController
{
public ActionResult Index()
{
var viewmodel = new Myviewmodel();
viewmodel.Somethings = Enumerable.Range(1,12).ToList();
return View(viewmodel);
}
}
视图(Razor)：
@Html.DropDownListFor(x => x.SelectedSomething,new SelectList(Model.Somethings,Model.SelectedSomething),"Select an Option")
这将“工作”,但不会为select中的任何已渲染的选项元素设置值：
<select>
<option value="">Select an Option</option>
<option>1</option>
<option>2</option>
<option>3</option>
<option>4</option>
<option>5</option>
<option>6</option>
<option>7</option>
<option>8</option>
<option>9</option>
<option>10</option>
<option>11</option>
<option>12</option>
</select>
我知道使用属性名称来渲染选项元素中的值和文本的SelectList constructor,但是当使用像int这样的原始类型的集合时,它是没有用的(我可以看到).
题：
我知道我可以改变我的视图模型的IList< int>到IList< SelectListItem>,并创建SelectListItem对象来表示每个int,但这似乎有点可笑(因为我认为构造函数不应该将值留空,并且应该默认使用文本).我在这里缺少一些明显的东西,还是我不得不在这里离开使用原始类型？
解决方法
我使用扩展方法解决了这个问题,允许你在你的视图中写：
@Html.DropDownListFor(x => x.SelectedSomething,Model.Somethings.ToSelectList(n => n,v => v),"Select an Option")
对于int集合,您可能需要使用n => n.ToString()作为您的名称选择器.
这种方法的优点是可以将其用于任何类型的枚举.在你的例子中(使用整数列表),我们只需指定返回元素本身的lambdas,这将导致在渲染的选项列表中将文本和值设置为相同的值.
如果要避免在Web.config中导入扩展类的命名空间,请在viewmodel上声明返回SelectList的只读属性,然后从视图中访问该属性.
Web.config部分看起来像这样(注意,您需要为程序集创建一行,并为命名空间创建一行).另请注意,您的Views文件夹包含一个单独的Web.config,可以覆盖或扩展根Web.config中的定义.
<system.web>
<compilation debug="true" targetFramework="4.0" batch="true">
<assemblies>
<add assembly="My.Web.Stuff" />
</assemblies>
</compilation>
<pages>
<namespaces>
<add namespace="My.Web.Stuff.Extensions" />
</namespaces>
</pages>
</system.web>
这是扩展方法的实现：
/// <summary>
/// Extension methods on IEnumerable.
/// </summary>
public static class SelectListExtensions
{
/// <summary>
/// Converts the source sequence into an IEnumerable of SelectListItem
/// </summary>
/// <param name = "items">Source sequence</param>
/// <param name = "nameSelector">Lambda that specifies the name for the SelectList items</param>
/// <param name = "valueSelector">Lambda that specifies the value for the SelectList items</param>
/// <returns>IEnumerable of SelectListItem</returns>
public static IEnumerable<SelectListItem> ToSelectList<TItem,TValue>( this IEnumerable<TItem> items,Func<TItem,TValue> valueSelector,string> nameSelector )
{
return items.ToSelectList( valueSelector,nameSelector,x => false );
}
/// <summary>
/// Converts the source sequence into an IEnumerable of SelectListItem
/// </summary>
/// <param name = "items">Source sequence</param>
/// <param name = "nameSelector">Lambda that specifies the name for the SelectList items</param>
/// <param name = "valueSelector">Lambda that specifies the value for the SelectList items</param>
/// <param name = "selectedItems">Those items that should be selected</param>
/// <returns>IEnumerable of SelectListItem</returns>
public static IEnumerable<SelectListItem> ToSelectList<TItem,string> nameSelector,IEnumerable<TValue> selectedItems )
{
return items.ToSelectList( valueSelector,x => selectedItems != null && selectedItems.Contains( valueSelector( x ) ) );
}
/// <summary>
/// Converts the source sequence into an IEnumerable of SelectListItem
/// </summary>
/// <param name = "items">Source sequence</param>
/// <param name = "nameSelector">Lambda that specifies the name for the SelectList items</param>
/// <param name = "valueSelector">Lambda that specifies the value for the SelectList items</param>
/// <param name = "selectedValueSelector">Lambda that specifies whether the item should be selected</param>
/// <returns>IEnumerable of SelectListItem</returns>
public static IEnumerable<SelectListItem> ToSelectList<TItem,bool> selectedValueSelector )
{
return from item in items
let value = valueSelector( item )
select new SelectListItem
{
Text = nameSelector( item ),Value = value.ToString(),Selected = selectedValueSelector( item )
};
}
}
