摺疊分組的DataGrid

PagedCollectionView pcv = this._dataGrid.ItemsSource as PagedCollectionView;

_dataGrid.UpdateLayout();

foreach (CollectionViewGroup group in pcv.Groups)
{
    foreach (var item in @group.Items)
    {
        if (item is CollectionViewGroup)
        {
            //_dataGrid.ScrollIntoView(item, null);
            _dataGrid.CollapseRowGroup((CollectionViewGroup)item, true);
        }
    }
}