Problem to get value

                                WorksheetPart worksheetPart = (WorksheetPart)workbookPart.GetPartById(sheet.Id);
                                WorkbookStylesPart wstylePart = workbookPart.WorkbookStylesPart;
                                Stylesheet ss = wstylePart.Stylesheet;

                                foreach (Cell cell in worksheetPart.Worksheet.Descendants<Cell>())
                                {
                                    if (cell.StyleIndex != null)
                                    {
                                    ...

Many Thanks & Best Regards, Hua Min