Attempting to perform a ConsolidationFunction on the same column used in GroupBy causes the subtotal to be overwritten by the aggregation label. Sample code:
sheet.Cells.Subtotal(ca, colNum, ConsolidationFunction.CountNums, new int[] { colNum }, true, false, true);
Essentially I'm trying to count the number of items in each group, but I can't use other columns because they might not necessarily contain values, or I might be using them for additional counts.
What I would like to see is shown in the expected results, which is how Excel 2010 creates the summary lines when using the Excel subtotal function.