private DataGridCollectionViewGroup CreateSubGroup(object groupName, int level, ObservableCollection <GroupDescription> groupByList,
List <GroupSortComparer> groupSortComparers)
{
// If sortComparers is null, we are in massive group creation, no order check.
DataGridCollectionViewGroup group = new DataGridCollectionViewGroup(groupName, this, m_nextSubGroupUnsortedIndex);
unchecked
{
m_nextSubGroupUnsortedIndex++;
}
int index;
if (groupSortComparers == null)
{
Debug.Assert(this.ProtectedItemCount == this.ProtectedItems.Count);
index = this.ProtectedItemCount;
}
else
{
index = this.BinarySearchGroup(group, groupSortComparers[level]);
if (index < 0)
{
index = ~index;
}
}
level++;
if (level < groupByList.Count)
{
group.SetSubGroupBy(groupByList[level]);
group.CreateFixedGroupNames(level, groupByList, groupSortComparers);
}
this.InsertGroup(index, group);
return(group);
}