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Gets or sets the location of the summary rows in the outline.
Use this property to determine whether summary rows are displayed above or below the detail rows for grouped data in the worksheet outline.
SummaryRow SummaryRow { get; set; }
Property SummaryRow As SummaryRow
worksheet.Range["2:5"].Group();
IOutline outline = worksheet.Outline;
outline.SummaryRow = SummaryRow.Above;
SummaryRow summaryRow = outline.SummaryRow;