有什么方法可以获取ItemsControl在WPF中的当前项的索引吗？
例如，我想做这样的事情：
<ItemsControl>
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBox Text="{Binding current_index}">
</TextBox>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
这样之后，第一个TextBox 将显示文本"0"，第二个"1"，第三个"2" ...。
【问题讨论】：
标签： c# wpf data-binding itemscontrol
我建议看看：
WPF ItemsControl the current ListItem Index in the ItemsSource
它解释了如何解决 ItemsControl 上没有内置 Index 属性这一事实。
编辑：
我尝试了以下代码：
<Window.Resources>
<x:Array Type="{x:Type sys:String}" x:Key="MyArray">
<sys:String>One</sys:String>
<sys:String>Two</sys:String>
<sys:String>Three</sys:String>
</x:Array>
</Window.Resources>
<ItemsControl ItemsSource="{StaticResource MyArray}" AlternationCount="100" >
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Path=(ItemsControl.AlternationIndex),
RelativeSource={RelativeSource TemplatedParent},
StringFormat={}Index is {0}}">
</TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl >
并获得一个包含三个 TextBlock 的窗口，例如：
[Index is 0]
[Index is 1]
[Index is 2]
【讨论】：
我如何获得 ItemIndex
<ItemsControl>
<ItemsControl.Resources>
<CollectionViewSource x:Key="ProductItems" Source="{Binding SelectedScanViewModel.Products}">
<CollectionViewSource.SortDescriptions>
<componentModel:SortDescription PropertyName="ProductName" Direction="Ascending"/>
</CollectionViewSource.SortDescriptions>
</CollectionViewSource>
</ItemsControl.Resources>
<ItemsControl.ItemsSource>
<Binding Source="{StaticResource ProductItems}"/>
</ItemsControl.ItemsSource>
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel HorizontalAlignment="Center">
<TextBlock Text="{Binding ProductName}" HorizontalAlignment="Center" />
<TextBox Name="txtFocus" Text="{Binding Qty}" MinWidth="80" HorizontalAlignment="Center"
behaviors:SelectTextOnFocus.Active="True">
<TextBox.TabIndex>
<MultiBinding Converter="{StaticResource GetIndexMultiConverter}" ConverterParameter="0">
<Binding Path="."/>
<Binding RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}" Path="ItemsSource"/>
</MultiBinding>
</TextBox.TabIndex>
</TextBox>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Columns="{Binding SelectedScanViewModel.Products.Count}"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
还有转换器：
public class GetIndexMultiConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
var collection = (ListCollectionView)values[1];
var itemIndex = collection.IndexOf(values[0]);
return itemIndex;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException("GetIndexMultiConverter_ConvertBack");
}
}
通过这种方式，您可以将每种类型的集合绑定到 ItemSource，并将其更改为 ListCollectionView。因此转换器适用于不同的集合类型。
xmlns:componentModel="clr-namespace:System.ComponentModel;assembly=WindowsBase"
【讨论】：
<TextBox.Text>），您将需要从Convert 方法返回一个字符串，可以使用return itemIndex.ToString() 或（更多一般）return System.Convert.ChangeType(itemIndex, targetType).
看看这个
<ItemsControl ItemsSource="{Binding Items}" Name="lista">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Vertical">
<TextBlock>
<TextBlock.Text>
<MultiBinding Converter="{StaticResource converter}">
<Binding Path="."/>
<Binding ElementName="lista" Path="ItemsSource"/>
</MultiBinding>
</TextBlock.Text>
</TextBlock>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
转换器看起来像这样
public class conv : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
ObservableCollection<string> lista = (ObservableCollection<string>)values[1];
return String.Concat(lista.IndexOf(values[0].ToString()), " ", values[0].ToString());
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
}
因此
【讨论】：
如果您的目标是让 ItemTemplate 中的按钮正常工作，我会使用 DataContext。您还应该能够使用 LINQ 从 DataContext 和 ItemsSource 中找到索引。
如果使用命令
Command="{Binding DataContext.TestCmd, ElementName=Parent_UC}"
CommandParameter="{Binding DataContext, RelativeSource={RelativeSource Mode=Self}}"
如果使用事件，请使用发送者。
private void Button_Click(object sender, System.Windows.RoutedEventArgs e)
{
if(sender is Button b)
{
if(b.DataContext is ClassType t)
{ enter code here }
}
}
【讨论】：
我是通过计算添加元素索引的转换器完成的。
它只能以一种方式工作。如果您以某种方式删除项目或更改集合，您应该使用其他东西。 你应该为每个集合创建单独的转换器，哪些元素需要被索引。
public class LineMultiplierConverter : IValueConverter
{
private int m_lineIndex = 0;
Line m_curentLine = null;
/// <summary>
/// Base value that will be multiplied
/// </summary>
public double BaseValue { get; set; }
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var line = value as Line;
if (line == null)
return BaseValue;
bool newLine = line != m_curentLine; //check the reference because this method will called twice on one element by my binding
if (newLine)
{
m_lineIndex++;
m_curentLine = line;
}
return BaseValue * m_lineIndex;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
我是这样在xaml中使用的
<UserControl.Resources>
<sys:Double x:Key="BusinessRowHeight">22</sys:Double>
<local:LineMultiplierConverter x:Key="LineXConverter" BaseValue="{StaticResource BusinessRowHeight}" />
</UserControl.Resources>
<ItemsControl Grid.Row="1" ItemsSource="{Binding CarBusiness}" Margin="0 5 0 0">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Line StrokeThickness="1" Stroke="LightGray"
X1="0"
Y1="{Binding RelativeSource={RelativeSource Self}, Converter={StaticResource LineXConverter}}"
X2="{Binding RelativeSource={RelativeSource AncestorType=ItemsControl, Mode=FindAncestor}, Path=ActualWidth}"
Y2="{Binding RelativeSource={RelativeSource Self}, Converter={StaticResource LineXConverter}}"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
这为我为集合中的每个元素绘制了一条线，其中 X 坐标的 BaseValue 偏移量。
【讨论】：
有一种方法可以在没有转换器的情况下执行此操作，并且能够在集合中包含重复项，但这意味着您必须维护一个有组织的列表，该列表还使用 KeyValuePair<int, T> 作为列表项类型来存储索引.
这是一个字符串列表的示例实现。它将显示按钮内的文本并将索引绑定到命令参数：
#region Items
public static readonly DependencyProperty ItemsProperty =
DependencyProperty.Register("Items", typeof(ObservableCollection<string>), typeof(CulturePicker),
new FrameworkPropertyMetadata(new ObservableCollection<string>(),
FrameworkPropertyMetadataOptions.None,
new PropertyChangedCallback(OnItemsChanged)));
public ObservableCollection<string> Items
{
get { return (ObservableCollection<string>)GetValue(ItemsProperty); }
set { SetValue(ItemsProperty, value); }
}
private static void OnItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
CulturePicker _this = (CulturePicker)d;
ObservableCollection<string> oldItems = (ObservableCollection<string>)e.OldValue;
ObservableCollection<string> newItems = _this.Items;
if (oldItems != null)
{
oldItems.CollectionChanged -= this.Items_CollectionChanged;
}
List<KeyValuePair<int, string>> organizedItems = new List<KeyValuePair<int, string>>();
for (int i = 0; i < newItems.Count; i++)
{
organizedItems.Add(new KeyValuePair<int, string>(i, newItems[i]));
}
this.OrganizedItems = organizedItems;
newItems.CollectionChanged += this.Items_CollectionChanged;
}
private void Items_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
List<KeyValuePair<int, string>> organizedItems = new List<KeyValuePair<int, string>>();
for (int i = 0; i < e.NewItems.Count; i++)
{
organizedItems.Add(new KeyValuePair<int, string>(i, (string)e.NewItems[i]));
}
this.OrganizedItems = organizedItems;
}
#endregion
#region OrganizedItems
/// <summary>
/// OrganizedItems Dependency Property
/// </summary>
private static readonly DependencyProperty OrganizedItemsProperty =
DependencyProperty.Register("OrganizedItems", typeof(List<KeyValuePair<int, string>>), typeof(CulturePicker),
new FrameworkPropertyMetadata((List<KeyValuePair<int, string>>)null,
FrameworkPropertyMetadataOptions.None,
new PropertyChangedCallback(OnOrganizedItemsChanged)));
/// <summary>
/// Gets or sets the OrganizedItems property. This dependency property
/// indicates an organized dictionary with the index of the Items as key and the region itself as value.
/// </summary>
private List<KeyValuePair<int, string>> OrganizedItems
{
get { return (List<KeyValuePair<int, string>>)GetValue(OrganizedItemsProperty); }
set { SetValue(OrganizedItemsProperty, value); }
}
/// <summary>
/// Handles changes to the OrganizedItems property.
/// </summary>
private static void OnOrganizedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
CulturePicker _this = (CulturePicker)d;
List<KeyValuePair<int, string>> oldOrganizedItems = (List<KeyValuePair<int, string>>)e.OldValue;
List<KeyValuePair<int, string>> newOrganizedItems = _this.OrganizedItems;
}
#endregion
<UserControl ...
Name="_">
...
<ItemsControl ItemsSource="{Binding OrganizedItems, ElementName=_}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button Command="{Binding Command, ElementName=_}"
CommandParameter="{Binding Key}"
Text="{Binding Value}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
...
在 XAML 中，键是索引，值是实际项目，在本例中是字符串。 Command 属性本身不包含在此示例中。另请注意，它会在源列表发生任何更改时重新创建有组织的列表，这将触发重新渲染并导致大列表运行缓慢。
【讨论】：