wpf listcollectionview grouping by multiple columns

public void GroupByMulti(ListCollectionView _list, string[] _properties)
{
    var groupProperty = _list.GroupDescriptions.FirstOrDefault();
    if (groupProperty == null)
    {
        foreach (string _property in _properties)
        {
            _list.GroupDescriptions.Add(new PropertyGroupDescription(_property));
        }
    }
    else
    {
        for (int i = 1; i < _properties.Length; i++)
        {
            _list.GroupDescriptions.Add(new PropertyGroupDescription(_properties[i]));
        }
    }
}