Wie man eine Datei mit NPOI liest

Question

Ich fand NPOI ist sehr gut, um Excel-Dateien mit C# zu schreiben.

Aber ich möchte Excel-Dateien in C# öffnen, lesen und ändern.

Wie kann ich das tun?

Answer 1

private static ISheet GetFileStream(string fullFilePath)
    {
        var fileExtension = Path.GetExtension(fullFilePath);
        string sheetName;
        ISheet sheet = null;
        switch (fileExtension)
        {
            case ".xlsx":
                using (var fs = new FileStream(fullFilePath, FileMode.Open, FileAccess.Read))
                {
                    var wb = new XSSFWorkbook(fs);
                    sheetName = wb.GetSheetAt(0).SheetName;
                    sheet = (XSSFSheet) wb.GetSheet(sheetName);
                }
                break;
            case ".xls":
                using (var fs = new FileStream(fullFilePath, FileMode.Open, FileAccess.Read))
                {
                    var wb = new HSSFWorkbook(fs);
                    sheetName = wb.GetSheetAt(0).SheetName;
                    sheet = (HSSFSheet) wb.GetSheet(sheetName);
                }
                break;
        }
        return sheet;
    }

    private static DataTable GetRequestsDataFromExcel(string fullFilePath)
    {
        try
        {
            var sh = GetFileStream(fullFilePath);
            var dtExcelTable = new DataTable();
            dtExcelTable.Rows.Clear();
            dtExcelTable.Columns.Clear();
            var headerRow = sh.GetRow(0);
            int colCount = headerRow.LastCellNum;
            for (var c = 0; c < colCount; c++)
                dtExcelTable.Columns.Add(headerRow.GetCell(c).ToString());
            var i = 1;
            var currentRow = sh.GetRow(i);
            while (currentRow != null)
            {
                var dr = dtExcelTable.NewRow();
                for (var j = 0; j < currentRow.Cells.Count; j++)
                {
                    var cell = currentRow.GetCell(j);

                    if (cell != null)
                        switch (cell.CellType)
                        {
                            case CellType.Numeric:
                                dr[j] = DateUtil.IsCellDateFormatted(cell)
                                    ? cell.DateCellValue.ToString(CultureInfo.InvariantCulture)
                                    : cell.NumericCellValue.ToString(CultureInfo.InvariantCulture);
                                break;
                            case CellType.String:
                                dr[j] = cell.StringCellValue;
                                break;
                            case CellType.Blank:
                                dr[j] = string.Empty;
                                break;
                        }
                }
                dtExcelTable.Rows.Add(dr);
                i++;
                currentRow = sh.GetRow(i);
            }
            return dtExcelTable;
        }
        catch (Exception e)
        {
            throw;
        }
    }

Answer 2

Da Sie darum gebeten haben, zu lesen und ändern die xls-Datei habe ich die Antwort von @mj82 an Ihre Bedürfnisse angepasst.

HSSFWorkbook hat nicht Save Methode, aber sie hat auch Write zu einem Strom.

static void Main(string[] args)
        {
            string filepath = @"C:\test.xls";

            HSSFWorkbook hssfwb;

            using (FileStream file = new FileStream(filepath, FileMode.Open, FileAccess.Read))
            {
                hssfwb = new HSSFWorkbook(file);
            }

            ISheet sheet = hssfwb.GetSheetAt(0);

            for (int row = 0; row <= sheet.LastRowNum; row++)
            {
                if (sheet.GetRow(row) != null) //null is when the row only contains empty cells 
                {
                    // Set new cell value
                    sheet.GetRow(row).GetCell(0).SetCellValue("foo");
                    Console.WriteLine("Row {0} = {1}", row, sheet.GetRow(row).GetCell(0).StringCellValue);
                }
            }

            // Save the file
            using (FileStream file = new FileStream(filepath, FileMode.Open, FileAccess.Write))
            {
                hssfwb.Write(file);
            }

            Console.ReadLine();
        }

Answer 3

Wenn Sie NPOI.Mapper nicht verwenden möchten, empfehle ich Ihnen, sich diese Lösung anzuschauen - sie kann Excel-Zellen in verschiedene Typen einlesen und verfügt über eine einfache Importhilfe: https://github.com/hidegh/NPOI.Extensions

var data = sheet.MapTo<OrderDetails>(true, rowMapper =>
{
  // map singleItem
  return new OrderDetails()
  {
    Date = rowMapper.GetValue<DateTime>(SheetColumnTitles.Date),

    // use reusable mapper for re-curring scenarios
    Region = regionMapper(rowMapper.GetValue<string>(SheetColumnTitles.Region)),

    Representative = rowMapper.GetValue<string>(SheetColumnTitles.Representative),
    Item = rowMapper.GetValue<string>(SheetColumnTitles.Item),
    Units = rowMapper.GetValue<int>(SheetColumnTitles.Units),
    UnitCost = rowMapper.GetValue<decimal>(SheetColumnTitles.UnitCost),
    Total = rowMapper.GetValue<decimal>(SheetColumnTitles.Total),

    // read date and total as string, as they're displayed/formatted on the excel
    DateFormatted = rowMapper.GetValue<string>(SheetColumnTitles.Date),
    TotalFormatted = rowMapper.GetValue<string>(SheetColumnTitles.Total)
  };
});