我在主列表中有ListBox作为ListboxItem。在ListBox的一个项目中，我选择了一个项目。当我从其他项目ListBox中选择了另一个项目时，应清除此选择。代码如下：
<ListBox x:Name="lst" Grid.Row="3" BorderThickness="0" ScrollViewer.HorizontalScrollBarVisibility="Hidden" ItemsSource="{Binding MessageCollection}" ScrollViewer.CanContentScroll="False" >
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Vertical" Width="{Binding RelativeSource= {RelativeSource FindAncestor, AncestorType={x:Type Grid}},Path=ActualWidth}" HorizontalAlignment="Stretch">
<Border Background ="#ffffff" BorderBrush="#dddddd" BorderThickness="0,1,0,0" Height="30" >
<TextBlock Text="{Binding Date, StringFormat={}{0:dd MMMM yyyy}}" VerticalAlignment="Center" FontWeight="Bold" FontSize="12" FontFamily="Tahoma" Foreground="#7a7a7a" HorizontalAlignment="Center" />
</Border>
<ListBox x:Name="lstMsgs" HorizontalAlignment="Stretch" ScrollViewer.HorizontalScrollBarVisibility="Hidden" HorizontalContentAlignment="Stretch" ItemsSource="{Binding MessageList}" SelectedItem="{Binding DataContext.SelectedMessage,Mode=TwoWay,ElementName=me}" Background="Transparent" BorderThickness="0">
<ListBox.ItemTemplate>
<DataTemplate>
<Border x:Name="brdItem" BorderBrush="#dddddd" BorderThickness="0,1,0,0" >
<Border.Background>
<LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
<GradientStop Color="#f1f1f1" Offset="0"/>
<GradientStop Color="#efefef" Offset="1"/>
</LinearGradientBrush>
</Border.Background>
<Grid Height="30" HorizontalAlignment="Stretch" VerticalAlignment="Center" ScrollViewer.HorizontalScrollBarVisibility="Hidden" >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="10" />
<ColumnDefinition Width="30" />
<ColumnDefinition Width="10" />
<ColumnDefinition Width="120" />
<ColumnDefinition Width="10" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="10" />
<ColumnDefinition Width="100" />
<ColumnDefinition Width="30" />
</Grid.ColumnDefinitions>
<Image x:Name="img" Grid.Column="1" Visibility="Collapsed" HorizontalAlignment="Center" Source="Images\icon1.png" Stretch="None" Margin="10,0,0,0" />
<TextBlock Text="Ershad Sheikh" VerticalAlignment="Center" Foreground="#2b2a2a" FontSize="12" Grid.Column="3" />
<TextBlock Text="{Binding GroupMessage}" HorizontalAlignment="Left" Foreground="#7a7a7a" FontSize="11" Grid.Column="5" VerticalAlignment="Center" TextTrimming="CharacterEllipsis" />
<TextBlock Text="{Binding Date, StringFormat={}{0: hh:mm:ss tt}}" FontWeight="Bold" FontSize="12" Foreground="#2378a0" Grid.Column="7" VerticalAlignment="Center" HorizontalAlignment="Right" />
</Grid>
</Border>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=IsReplyPresent}" Value="True">
<Setter TargetName="img" Property="Visibility" Value="Visible" />
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Value="True">
<Setter TargetName="brdItem" Property="Background" Value="#e5e9eb" >
</Setter>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}"
Color="#e5e9eb"/>
<SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}"
Color="Transparent" />
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black"/>
</ListBox.Resources>
</ListBox>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}"
Color="#e5e9eb"/>
<SolidColorBrush x:Key="{x:Static SystemColors.ControlBrushKey}"
Color="Transparent" />
</ListBox.Resources>
</ListBox>
答案 0 :(得分：1)
只要null失去焦点，您就可以明确SelectedItem ListBox，即您必须处理LostFocus事件。
您可以将事件处理程序添加到ListBox并在后面的代码中处理事件。
XAML更改：
<ListBox x:Name="lstMsgs" HorizontalAlignment="Stretch" ScrollViewer.HorizontalScrollBarVisibility="Hidden" HorizontalContentAlignment="Stretch" ItemsSource="{Binding MessageList}" SelectedItem="{Binding DataContext.SelectedMessage,Mode=TwoWay,ElementName=me}" Background="Transparent" BorderThickness="0" LostFocus="lstMsgs_LostFocus">
代码背后：
private void lstMsgs_LostFocus(object sender, RoutedEventArgs e)
{
ListBox listBox = sender as ListBox;
if (listBox != null)
{
listBox.SelectedItem = null;
}
}
方法2：
使用DependencyProperty处理LostFocus事件可以获得相同的结果。
ListBoxExtension.cs
using System.Windows;
using System.Windows.Controls;
namespace WpfApplication1
{
public static class ListBoxExtension
{
public static readonly DependencyProperty NullSelectedItemOnLostFocusProperty =
DependencyProperty.RegisterAttached("NullSelectedItemOnLostFocus", typeof(bool), typeof(ListBoxExtension), new UIPropertyMetadata(false, OnNullSelectedItemOnLostFocusChanged));
public static bool GetNullSelectedItemOnLostFocus(DependencyObject d)
{
return (bool)d.GetValue(NullSelectedItemOnLostFocusProperty);
}
public static void SetNullSelectedItemOnLostFocus(DependencyObject d, bool value)
{
d.SetValue(NullSelectedItemOnLostFocusProperty, value);
}
private static void OnNullSelectedItemOnLostFocusChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
bool nullSelectedItemOnLostFocus = (bool)e.NewValue;
ListBox listBox = d as ListBox;
if (listBox != null)
{
if (nullSelectedItemOnLostFocus)
listBox.LostFocus += NullSelectedItem;
else
listBox.LostFocus -= NullSelectedItem;
}
}
public static void NullSelectedItem(object sender, RoutedEventArgs e)
{
ListBox listBox = sender as ListBox;
if (listBox != null)
{
listBox.SelectedItem = null;
}
}
}
}
XAML更改1：添加存在ListBoxExtension类的命名空间 - xmlns：loc =“clr-namespace：WpfApplication1”
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:loc="clr-namespace:WpfApplication1"
Title="MainWindow" Height="350" Width="525">
XAML更改2：更改DependencyProperty - loc：ListBoxExtension.NullSelectedItemOnLostFocus =“True”
<ListBox x:Name="lstMsgs" HorizontalAlignment="Stretch" ScrollViewer.HorizontalScrollBarVisibility="Hidden" HorizontalContentAlignment="Stretch" ItemsSource="{Binding MessageList}" SelectedItem="{Binding DataContext.SelectedMessage,Mode=TwoWay,ElementName=me}" Background="Transparent" BorderThickness="0" loc:ListBoxExtension.NullSelectedItemOnLostFocus="True">