How to populate CategoryRingtone in LongListSelector group by “GroupName” and header template contain “GroupIconPath” and “GroupName”?

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Windows-Phone-8

I think my problem fully expressed by my question. I could create group with the help of http://www.geekchamp.com/articles/the-new-longlistselector-control-in-windows-phone-8-sdk-in-depth but how can i pass "GroupIconPath" to use in header template.

public class CategoryCollection
    {
      public string GroupName { get; set; }
      public string GroupIconPath { get; set; }
      public List<Category> CategoryRingtone { get; set; }
      public CategoryCollection()
      {
          CategoryRingtone = new List<Category>();
      }
    }

public  class Category
    {
        public string id { get; set; }
        public string name { get; set; }
        public string islock { get; set; }
    }

<phone:LongListSelector.GroupHeaderTemplate>
<DataTemplate>
<StackPanel Height="80" Margin="0" Orientation="Horizontal" HorizontalAlignment="Stretch">
<TextBlock Text="{Binding GroupName }" FontSize="32" Foreground="Green" />
<Image Source="{Binding GroupIconPath}"/>
</StackPanel>
</DataTemplate>
</phone:LongListSelector.GroupHeaderTemplate>

<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<StackPanel Height="70" Margin="0,0,0,1" VerticalAlignment="Center">
<StackPanel.Background>
<ImageBrush ImageSource="Assets/ImageButton/list-bar.png"/>
</StackPanel.Background>
<TextBlock Text="{Binding name}" VerticalAlignment="Center" FontSize="30" Height="60" Style="{StaticResource PhoneTextNormalStyle}"/>

</StackPanel>

</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>