OpenXML - Excel -traverse and write the value in empty cells

Question

I have to read excel from blob storage(URL is given) and insert some default values in empty cells and upload the excel again in blob without saving it in local anywhere ie insert some dummy values in empty cells. Till now I'm able to traverse the nonempty cells but unable to traverse the empty cells.

     //Passing the steam here by using WebClient to read form an URL
            using (SpreadsheetDocument spreadSheetDocument = SpreadsheetDocument.Open(stream, false))
                            {
                                string cellValue;
                                int columnNumber = -1;
                                int rowNumber = 0;

                                WorkbookPart workBookPart = spreadSheetDocument.WorkbookPart;
//selecting the particular sheet 
                                Sheet workSheet = workBookPart.Workbook.Descendants<Sheet>().Where(s =>
                                s.Name.Value.Equals("Sheet1")).FirstOrDefault();
                                WorksheetPart workSheetPart = (WorksheetPart)(workBookPart.GetPartById(workSheet.Id));
                                SheetData sheetData = workSheetPart.Worksheet.Elements<SheetData>().First();
                            foreach (Row r in sheetData.Elements<Row>())
                            {
                                rowNumber++;
                                columnNumber = -1;
                                foreach (Cell c in r.Elements<Cell>())
                                {
                                    string letter;
                                    letter = GetColumnLetter(columnNumber);

                                    while (c.CellReference.ToString().Substring(0, letter.Length) != letter)
                                    {
                                        columnNumber++;
                                        letter = GetColumnLetter(columnNumber);
                                    }

                                    cellValue = GetCellValue(workBookPart, "Sheet1", c.CellReference);

                                    columnNumber++;
                                }
                            }
                            }
                        }
    //Return the cell value
            public static string GetCellValue(WorkbookPart workBookPart, string sheetName, string addressName)
                    {
                        string value = null;
                        Sheet mySheet = workBookPart.Workbook.Descendants<Sheet>().Where(s => s.Name == sheetName).FirstOrDefault();
                        if (mySheet == null)
                        {
                            throw new ArgumentException("cannot find the following sheet: " + mySheet);
                        }
                        WorksheetPart wsPart = (WorksheetPart)(workBookPart.GetPartById(mySheet.Id));
                        Cell myCell = wsPart.Worksheet.Descendants<Cell>().Where(c => c.CellReference == addressName).FirstOrDefault();
                        if (myCell != null)
                        {
                            value = myCell.InnerText;
                            if (myCell.DataType != null)
                            {
                                switch (myCell.DataType.Value)
                                {
                                    case CellValues.SharedString:
                                        var stringTable = workBookPart.GetPartsOfType<SharedStringTablePart>().FirstOrDefault();
                                        if (stringTable != null)
                                        {
                                            value = stringTable.SharedStringTable.ElementAt(int.Parse(value)).InnerText;
                                        }
                                        if (stringTable == null)
                                        {
                                            value = "";
                                        }
                                        break;
                                    case CellValues.Boolean:
                                        switch (value)
                                        {
                                            case "0":
                                                value = "FALSE";
                                                break;
                                            case "1":
                                                value = "TRUE";
                                                break;
                                        }
                                        break;
                                }
                            }
                        }
                        return value;
                    }

Answer 1

In your function GetCellValue you initialize the return value like

string value = null;

Try to do instead:

 string value = string.Empty;