WPF的树通过绑定后如何实现展开折叠事件？

我目前的代码是<TreeView Margin="5,5,5,5" Name="treeView1" ItemsSource="{Binding Path=AaaNode}">
                    <TreeView.Resources>
                        <HierarchicalDataTemplate DataType="{x:Type y:fffTreeNode}" ItemsSource="{Binding Children}">
                            <StackPanel Orientation="Horizontal">
                                <Image Source="{Binding Image}"></Image>
                                <CheckBox x:Name="bbbbCheckBox" IsChecked="{Binding Path=IsChecked}" Margin="3" />
                                <TextBlock Text="{Binding Text}" />
                            </StackPanel>
                        </HierarchicalDataTemplate>
                        <Style TargetType="{x:Type TreeViewItem}">
                            <Setter Property="IsExpanded" Value="{Binding Path=IsExpanded}" />
                            <Setter Property="IsSelected" Value="{Binding Path=IsSelectedItem}"/>
                        </Style>
                        
                    </TreeView.Resources>
                </TreeView>