我创建了一个包含以下DataTemplate的列表框控件
<DataTemplate x:Key="lb_Itemtemplate">
<DockPanel>
<TextBlock Text="{Binding}" DockPanel.Dock="Left" />
<Button DockPanel.Dock="Right" Template="{StaticResource ButtonTemplate }"
Width="20" Margin=" 0,1,1,10" >Delete </Button>
<Button DockPanel.Dock="Right" Template="{StaticResource ButtonTemplate }"
Width="20" Margin="0,1,1,10" >Highlight </Button>
</DockPanel>
</DataTemplate>
<ListBox Name="listBox1" Grid.Column="0" Grid.Row="1"
DataContext="{Binding ElementName=cb_fields, Path=SelectedItem}"
ItemsSource="{Binding Path=PositiveXPathExpressions}"
ItemTemplate="{StaticResource lb_Itemtemplate}" />
我想在用户点击“删除”按钮时删除“PositiveXPathExpressions”集合中的元素,但我如何决定必须删除哪个元素?