How to add a checkbox to every group header? (and handle click/change event)

Hi Vikram,

As you have seen, the DataContext for the Checkbox in the HeaderPrefixArea is not really useful for your requirement.  I think a better option is to travel up the visual tree from the Checkbox and find the HeaderPresenter.  From there you can get the HeaderRecord and then all the GroupByRecords underneath it.  The behavior might look something like this:

public class GroupByCheckBoxBehavior_Header : Behavior<CheckBox>
{
    private HeaderRecord _header;
    public HeaderRecord Header
    {
        get
        {
            if (_header == null)
            {
                var presenter = (HeaderPresenter)Utilities.GetAncestorFromType(AssociatedObject, typeof(HeaderPresenter), false);
                _header = presenter.DataContext as HeaderRecord;
            }
            return _header;
        }
    }
    protected override void OnAttached()
    {
        AssociatedObject.Checked += AssociatedObject_Checked;
        AssociatedObject.Unchecked += AssociatedObject_Unchecked;

        base.OnAttached();
    }

    private void AssociatedObject_Checked(object sender, RoutedEventArgs e)
    {
        if (Header.RecordManager.HasGroups)
        {
            foreach (var groupRecord in Header.RecordManager.Groups)
            {
                groupRecord.Tag = true;
            }
        }
    }

    private void AssociatedObject_Unchecked(object sender, RoutedEventArgs e)
    {
        if (Header.RecordManager.HasGroups)
        {
            foreach (var groupRecord in Header.RecordManager.Groups)
            {
                groupRecord.Tag = false;
            }
        }
    }
}

In the Infragistics.Windows.Utilities class there is a method called GetAncestorFromType which I use to traverse up the visual tree and find a specific element.