WPF中Expander与ListBox(ItemsControl)嵌套中的问题

1. 当ListBox放在Expander中时，为了要实现实时更新数据的效果，这里使用了

ObservableCollection类型来作为数据源，

初始的简单例子如下：只有一个ListBox

xaml文件

 1 <Window x:Class="ObservableCollectionAddRemoveDemo.MainWindow"
 2         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 3         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 4         Title="MainWindow" Height="350" Width="525">
 5     <Grid>
 6         <ListBox BorderBrush="Red" BorderThickness="2" HorizontalAlignment="Left" Height="Auto" Margin="37,32,0,0" VerticalAlignment="Top" Width="157" ItemsSource="{Binding}">
 7             <ListBox.ItemContainerStyle>
 8                 <Style TargetType="ListBoxItem" >
 9                     <Setter Property="Opacity" Value="0.5" />
10                     <Setter Property="Opacity" Value="0.5" />
11                     <Setter Property="MaxHeight" Value="75" />
12                     <Setter Property="Background" Value="Green"/>
13                     <Style.Triggers>
14                         <Trigger Property="IsSelected" Value="True">
15                             <Setter Property="Opacity" Value="1.0" />
16                         </Trigger>
17                     </Style.Triggers>
18                 </Style>
19             </ListBox.ItemContainerStyle>
20         </ListBox>
21         <ItemsControl HorizontalAlignment="Left" Height="auto" Margin="210,32,0,0" VerticalAlignment="Top" Width="157" ItemsSource="{Binding}">
22             <ItemsControl.ItemContainerStyle>
23                 <Style TargetType="ContentPresenter">
24                     <Setter Property="Opacity" Value="0.5" />
25                     <Setter Property="Opacity" Value="0.5" />
26                     <Setter Property="MaxHeight" Value="75" />
27                 </Style>
28             </ItemsControl.ItemContainerStyle>
29         </ItemsControl>
30         <Button Content="Add" HorizontalAlignment="Left" Margin="398,65,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>
31         <Button Content="Remove" HorizontalAlignment="Left" Margin="398,160,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click_Remove"/>
32
33     </Grid>
34 </Window>

后台文件

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Collections.ObjectModel;
 4 using System.Linq;
 5 using System.Text;
 6 using System.Threading.Tasks;
 7 using System.Windows;
 8 using System.Windows.Controls;
 9 using System.Windows.Data;
10 using System.Windows.Documents;
11 using System.Windows.Input;
12 using System.Windows.Media;
13 using System.Windows.Media.Imaging;
14 using System.Windows.Navigation;
15 using System.Windows.Shapes;
16
17 namespace ObservableCollectionAddRemoveDemo
18 {
19     /// <summary>
20     /// Interaction logic for MainWindow.xaml
21     /// </summary>
22     public partial class MainWindow : Window
23     {
24         public ObservableCollection<String> list;
25         //public List<String> list;
26         public MainWindow()
27         {
28             InitializeComponent();
29             list = new ObservableCollection<string>() { "asda","12asdas","a22321","asda112323","xcvcvcxv","aasda","123123","asdasdasd"};
30             this.DataContext = list;
31         }
32
33         private void Button_Click(object sender, RoutedEventArgs e)
34         {
35             int addNumber = new Random().Next(999);
36             list.Add(addNumber.ToString());
37         }
38
39
40         private void Button_Click_Remove(object sender, RoutedEventArgs e)
41         {
42             if (list.Count > 0)
43                 list.RemoveAt(0);
44         }
45     }
46 }

发现代码实现的很顺畅，无论是增删都能实时响应到界面中

2. 但当在ListBox外面套一个Expander时，问题就出现了，如下图：

在删除数据时，内容明显变少了，但属于删掉内容的位置确仍然保留在界面上！！！

解决的办法是：在Expander的 ContentPresenter外面套一个StackPanel，如下：

1  <StackPanel>
2          <ContentPresenter x:Name="ExpanderContent" ContentSource="Content"/>
3 </StackPanel>

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当将Expander放在ListBox中时也有可能会出现类似的问题：https://www.dotblogs.com.tw/ouch1978/archive/2011/03/11/wpf-expander-in-listbox.aspx