combobox在选中选项时变更选中图片的绑定写法

<!-- 边框样式 -->
                <ComboBox x:Name="BorderTypeComboBox" 
                          Margin="18,0,0,0"
                          Width="68" Height="25" 
                          Style="{StaticResource QujiaoComboBoxStyle}"
                          ItemsSource="{Binding BorderTypes}"
                          SelectedIndex="{Binding SelectedIndexBorderType}">
                    <!-- 下拉选项宽度设置 -->
                    <ComboBox.Resources>
                        <Style TargetType="Popup">
                            <Setter Property="Width" Value="1000"/>
                            <Setter Property="MinWidth" Value="154"/>
                        </Style>
                        <Style TargetType="ComboBoxItem">
                            <Setter Property="Width" Value="154"/>
                            <Setter Property="Height" Value="35"/>
                        </Style>
                    </ComboBox.Resources>
                    <ComboBox.ItemTemplate>
                        <DataTemplate>
                            <Grid>
                                <Image x:Name="img"  Source="{Binding Img}" Margin="5,0,5,0"  Width="145" Height="35"  HorizontalAlignment="Center" VerticalAlignment="Stretch"/>
                            </Grid>
                            <DataTemplate.Triggers>
                                <Trigger Property="IsMouseOver" Value="true">
                                    <Setter Property="Source" TargetName="img" Value="{Binding SelectedImg}"/>
                                </Trigger>
                                <Trigger Property="IsMouseOver" Value="False">
                                    <Setter Property="Source" TargetName="img" Value="{Binding Img}"/>
                                </Trigger>
                                <DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=IsSelected}" Value="true">
                                    <Setter Property="Source" TargetName="img" Value="{Binding SelectedImg}"/>
                                </DataTrigger>
                            </DataTemplate.Triggers>
                        </DataTemplate>
                    </ComboBox.ItemTemplate>
                </ComboBox>

其中

<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=TemplatedParent},Path=IsSelected}" Value="true">
    <Setter Property="Source" TargetName="img" Value="{Binding SelectedImg}"/>
</DataTrigger>
这部分RelativeSource={RelativeSource Mode=TemplatedParent}是指要绑定当前目标的上一级内容

这里因为是在ComboBox.ItemTemplate的DataTemplate中设置的数据绑定,所以父级就是ComboBoxItem本身