DataGrid 分组后有关问题

DataGrid 分组后问题
想要实现如下效果，使用DataGrid的分组功能基本都搞定，但是如果取消勾选一个charge, 确不能将Category的checkbox取消勾选。不知该如何解决


XAML：


                    <GroupStyle.ContainerStyle>
                        <Style TargetType="{x:Type GroupItem}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="{x:Type GroupItem}">
                                        <Expander  IsExpanded="{Binding DataContext.AreAllGroupsExpanded, RelativeSource={RelativeSource AncestorType={x:Type local:UserControl1}}, UpdateSourceTrigger= PropertyChanged}"
                                                  >
                                            <Expander.Header>
                                                <StackPanel Orientation="Horizontal">
                                                    <CheckBox Name="chGroup"  Tag="{Binding Path=Name}" Checked="CheckBox_Checked"></CheckBox>
                                                    <TextBlock Text="{Binding Path=Name}" />
                                                    
                                                </StackPanel>
                                            </Expander.Header>

                                            <Expander.Content>
                                                <ItemsPresenter />
                                            </Expander.Content>


                                        </Expander>

                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>