When grouping columns, SummaryColumns determines where the summary columns for the groups are located. By default the summary rows are located to the right of the groupings.

<p> public SummaryColumnsLocation SummaryColumns{ get; set; }</p>
<p>Public Property SummaryColumns() As SummaryColumnsLocation</p>

          //--- Get SummaryColumns
          Worksheet.SummaryColumnsLocation location = ws.SummaryColumns;

          //--- Set SummaryColumns
          ws.SummaryColumns = Worksheet.SummaryColumnsLocation.Left;
        
          '--- Get SummaryColumns
          Dim location As Worksheet.SummaryColumnsLocation = ws.SummaryColumns

          '--- Set SummaryColumns
          ws.SummaryColumns = Worksheet.SummaryColumnsLocation.Left