Existing spreadsheet document file create new cell in c#

Question

I have open existing spreadsheet document file. then this file inserts some cell in the particular index value.

how to insert the new cell in this open file.

DataTable dataTable = new DataTable();
               using (SpreadsheetDocument spreadSheetDocument = SpreadsheetDocument.Open(srcFile, false))
               {
                   WorkbookPart workbookPart = spreadSheetDocument.WorkbookPart;
                   IEnumerable<Sheet> sheets = spreadSheetDocument.WorkbookPart.Workbook.GetFirstChild<Sheets>().Elements<Sheet>();
                   string relationshipId = sheets.First().Id.Value;
                   WorksheetPart worksheetPart = (WorksheetPart)spreadSheetDocument.WorkbookPart.GetPartById(relationshipId);
                   Worksheet workSheet = worksheetPart.Worksheet;
                   SheetData sheetData = workSheet.GetFirstChild<SheetData>();
                   IEnumerable<Row> rows = sheetData.Descendants<Row>();

                   foreach (Cell cell in rows.ElementAt(0))
                   {
                       dataTable.Columns.Add(GetCellValue(spreadSheetDocument, cell));

                   }
                   ArrayList list = new ArrayList();
                   foreach (Row row in rows)
                   {
                       DataRow dataRow = dataTable.NewRow();
                       for (int i = 0; i < 1; i++)
                       {
                                   list.Add(GetCellValue(spreadSheetDocument, row.Descendants<Cell>().ElementAt(i)));
                       }
                   }
                    Row row1 = new Row() { RowIndex = 2U, Spans = new ListValue<StringValue>() };
                   Cell cell1 = new Cell()
                   {
                       CellReference = "A52",
                       DataType = CellValues.String,
                       CellValue = new CellValue("Microsoft")
                   };
                   Row r = new Row();
                   r.Append(cell1);
                   sheetData.AppendChild(r);
                   worksheetPart.Worksheet.Append(sheetData);
                   worksheetPart.Worksheet.Save();

               }

 problem in last 5 line how to insert new cell value in this existing file in c#