Windows Phone如何添加List View的组标题按钮的事件？

Question

在教程http://msdn.microsoft.com/zh-cn/library/windows/apps/xaml/hh780627.aspx中，如何将组按钮添加点击事件？

部分代码：

App.Xaml：

<Application
    x:Class="ItemsControlGroupingSnippets.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:ItemsControlGroupingSnippets">

    <Application.Resources>
        <ResourceDictionary>
            <DataTemplate x:Key="listViewItemTemplate">
                <StackPanel Width="320" Margin="10">
                    <StackPanel Orientation="Horizontal">
                        <TextBlock Text="{Binding Name}" FontWeight="Bold" Style="{StaticResource BaseTextBlockStyle}"
                       Margin="2,0,0,0"/>
                        <TextBlock Text="{Binding DueDate}" Style="{StaticResource BodyTextBlockStyle}" TextWrapping="NoWrap"
                       Margin="20,0,0,0"/>
                    </StackPanel>
                    <CheckBox Content="Complete" IsChecked="{Binding Complete}" IsEnabled="False"/>
                </StackPanel>
            </DataTemplate>

            <GroupStyle x:Key="listViewGroupStyle">
                <GroupStyle.HeaderTemplate>
                    <DataTemplate>
                        <Grid Background="LightGray"  >
                            <TextBlock Text='{Binding Key}' Foreground="Black" Margin="10"
                           Style="{StaticResource SubheaderTextBlockStyle}" />
                        </Grid>
                    </DataTemplate>
                </GroupStyle.HeaderTemplate>
            </GroupStyle>
        </ResourceDictionary>
    </Application.Resources>
</Application>

MainPage.Xaml：

        <ListView ItemsSource="{Binding Source={StaticResource cvsActivities}}"
          ItemTemplate="{StaticResource listViewItemTemplate}"
          GroupStyleSelector="{StaticResource listGroupStyleSelector}"
          Margin="120" Width="320"/>

MainPage.xaml.cs：

    public class ListGroupStyleSelector : GroupStyleSelector
    {
        protected override GroupStyle SelectGroupStyleCore(object group, uint level)
        {
            return (GroupStyle)App.Current.Resources["listViewGroupStyle"];
        }
    }