private ColumnGrouping(int numColumns, IEnumerable <int> indices)
{
this.numColumns = numColumns;
GroupingId = GroupingIdConverter.GetConverter(numColumns).GroupingIdFromIndices(indices.ToArray());
Indices = indices.ToImmutableArray();
}
public ColumnGrouping(int numColumns, int groupingId)
{
this.numColumns = numColumns;
GroupingId = groupingId;
Indices = GroupingIdConverter.GetConverter(numColumns).IndicesFromGroupingId(GroupingId).ToImmutableArray();
}