C# 使用DropDownListFor和基元类型列表的正确方法?
这是相关代码。请注意,我是在记事本++中完成的,而不是在工作中复制我的项目代码。如果我在其中拼错了一个类名,那么假设我的代码中没有拼错。没有编译错误 型号:C# 使用DropDownListFor和基元类型列表的正确方法?,c#,asp.net-mvc-3,razor,C#,Asp.net Mvc 3,Razor,这是相关代码。请注意,我是在记事本++中完成的,而不是在工作中复制我的项目代码。如果我在其中拼错了一个类名,那么假设我的代码中没有拼错。没有编译错误 型号: public class MyViewModel { public int SelectedSomething { get; set; } public IList<int> Somethings { get; set; } } 视图(剃须刀): 这将“起作用”,但不会在选择中的任何渲染选项元素上设置值: &
public class MyViewModel
{
public int SelectedSomething { get; set; }
public IList<int> Somethings { get; set; }
}
视图(剃须刀):
这将“起作用”,但不会在选择
中的任何渲染选项
元素上设置值:
<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>
选择一个选项
1.
2.
3.
4.
5.
6.
7.
8.
9
10
11
12
我知道在选项
元素中使用属性名来呈现值
和文本
,但在使用诸如int
之类的基元类型集合时(我可以看到),它是没有用的
问题:
我知道我可以将视图模型的
IList
更改为IList
,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,应该默认使用文本)。我是否遗漏了一些明显的内容,或者我将不得不放弃在这里使用基本类型?我使用扩展方法解决了这个问题,允许您在视图中编写以下内容:
@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()
作为名称选择器
这种方法的优点在于,您可以将其用于任何类型的可枚举数据。在您的示例中(使用整数列表),我们只需指定返回元素本身的lambda,这将导致文本和值在呈现选项列表中设置为相同的值
如果要避免在Web.config中导入extensions类的命名空间,请在ViewModel上声明一个只读属性,该属性返回SelectList,然后从视图中访问该属性
Web.config部分看起来像这样(请注意,您需要为程序集和命名空间创建一行)。还要注意,视图文件夹包含一个单独的Web.config,它可能会覆盖或扩展根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, Func<TItem, 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, TValue>( this IEnumerable<TItem> items, Func<TItem, TValue> valueSelector, Func<TItem, string> nameSelector, IEnumerable<TValue> selectedItems )
{
return items.ToSelectList( valueSelector, nameSelector, 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, TValue>( this IEnumerable<TItem> items, Func<TItem, TValue> valueSelector, Func<TItem, string> nameSelector, Func<TItem, bool> selectedValueSelector )
{
return from item in items
let value = valueSelector( item )
select new SelectListItem
{
Text = nameSelector( item ),
Value = value.ToString(),
Selected = selectedValueSelector( item )
};
}
}
//
///IEnumerable上的扩展方法。
///
公共静态类SelectListExtensions
{
///
///将源序列转换为SelectListItem的IEnumerable
///
///源序列
///Lambda,指定SelectList项的名称
///Lambda,指定SelectList项的值
///SelectListItem的IEnumerable
公共静态IEnumerable ToSelectList(此IEnumerable项、Func valueSelector、Func nameSelector)
{
返回items.ToSelectList(valueSelector,nameSelector,x=>false);
}
///
///将源序列转换为SelectListItem的IEnumerable
///
///源序列
///Lambda,指定SelectList项的名称
///Lambda,指定SelectList项的值
///应选择的项目
///SelectListItem的IEnumerable
公共静态IEnumerable ToSelectList(此IEnumerable项、Func valueSelector、Func nameSelector、IEnumerable selectedItems)
{
返回items.ToSelectList(valueSelector,nameSelector,x=>selectedItems!=null&&selectedItems.Contains(valueSelector(x));
}
///
///将源序列转换为SelectListItem的IEnumerable
///
///源序列
///Lambda,指定SelectList项的名称
///Lambda,指定SelectList项的值
///Lambda,指定是否应选择该项
///SelectListItem的IEnumerable
公共静态IEnumerable to SelectList(此IEnumerable项、Func valueSelector、Func nameSelector、Func selectedValueSelector)
{
从项目中的项目返回
让值=值选择器(项目)
选择新的SelectListItem
{
Text=名称选择器(项目),
Value=Value.ToString(),
Selected=selectedValueSelector(项目)
};
}
}
我喜欢它。我明天会在工作中使用它!代码看起来合法,标记为答案,谢谢!!
<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>
/// <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, Func<TItem, 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, TValue>( this IEnumerable<TItem> items, Func<TItem, TValue> valueSelector, Func<TItem, string> nameSelector, IEnumerable<TValue> selectedItems )
{
return items.ToSelectList( valueSelector, nameSelector, 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, TValue>( this IEnumerable<TItem> items, Func<TItem, TValue> valueSelector, Func<TItem, string> nameSelector, Func<TItem, bool> selectedValueSelector )
{
return from item in items
let value = valueSelector( item )
select new SelectListItem
{
Text = nameSelector( item ),
Value = value.ToString(),
Selected = selectedValueSelector( item )
};
}
}