Convert xlsx file to xls using NPOI in c#

Question

I\'ve a excel file in *.xlsx format. I want convert this file into *.xls format in my MVC Web application. In my application hosted server there is no Microsoft.Office packa

Answer 1

I found the solution based on the Andy's suggestion. Here is the source code which is customized to convert XLSX to XLS.

 public static class ConvertXLSXToXLS
{
    public static HSSFWorkbook ConvertWorkbookXSSFToHSSF(XSSFWorkbook source)
    {
        //Install-Package NPOI -Version 2.0.6
        HSSFWorkbook retVal = new HSSFWorkbook();
        for (int i = 0; i < source.NumberOfSheets; i++)
        {
            HSSFSheet hssfSheet = (HSSFSheet)retVal.CreateSheet(source.GetSheetAt(i).SheetName);

            XSSFSheet xssfsheet = (XSSFSheet)source.GetSheetAt(i);
            CopySheets(xssfsheet, hssfSheet, retVal);
        }
        return retVal;
    }

    private static void CopySheets(XSSFSheet source, HSSFSheet destination, HSSFWorkbook retVal)
    {
        int maxColumnNum = 0;
        Dictionary styleMap = new Dictionary();
        for (int i = source.FirstRowNum; i <= source.LastRowNum; i++)
        {
            XSSFRow srcRow = (XSSFRow)source.GetRow(i);
            HSSFRow destRow = (HSSFRow)destination.CreateRow(i);
            if (srcRow != null)
            {
                CopyRow(source, destination, srcRow, destRow, styleMap, retVal);
                if (srcRow.LastCellNum > maxColumnNum)
                {
                    maxColumnNum = srcRow.LastCellNum;
                }
            }
        }
        for (int i = 0; i <= maxColumnNum; i++)
        {
            destination.SetColumnWidth(i, source.GetColumnWidth(i));
        }
    }

    private static void CopyRow(XSSFSheet srcSheet, HSSFSheet destSheet, XSSFRow srcRow, HSSFRow destRow,
            Dictionary styleMap, HSSFWorkbook retVal)
    {
        // manage a list of merged zone in order to not insert two times a
        // merged zone
        List mergedRegions = new List();
        destRow.Height = srcRow.Height;
        // pour chaque row
        for (int j = srcRow.FirstCellNum; j <= srcRow.LastCellNum; j++)
        {
            XSSFCell oldCell = (XSSFCell)srcRow.GetCell(j); // ancienne cell
            HSSFCell newCell = (HSSFCell)destRow.GetCell(j); // new cell
            if (oldCell != null)
            {
                if (newCell == null)
                {
                    newCell = (HSSFCell)destRow.CreateCell(j);
                }
                // copy chaque cell
                CopyCell(oldCell, newCell, styleMap, retVal);
                // copy les informations de fusion entre les cellules
                CellRangeAddress mergedRegion = GetMergedRegion(srcSheet, srcRow.RowNum,
                        (short)oldCell.ColumnIndex);

                if (mergedRegion != null)
                {
                    CellRangeAddress newMergedRegion = new CellRangeAddress(mergedRegion.FirstRow,
                            mergedRegion.LastRow, mergedRegion.FirstColumn, mergedRegion.LastColumn);
                    if (IsNewMergedRegion(newMergedRegion, mergedRegions))
                    {
                        mergedRegions.Add(newMergedRegion);
                        destSheet.AddMergedRegion(newMergedRegion);
                    }

                    if (newMergedRegion.FirstColumn == 0 && newMergedRegion.LastColumn == 6 && newMergedRegion.FirstRow == newMergedRegion.LastRow)
                    {
                        HSSFCellStyle style2 = (HSSFCellStyle)retVal.CreateCellStyle();
                        style2.VerticalAlignment = VerticalAlignment.Center;
                        style2.Alignment = HorizontalAlignment.Left;
                        style2.FillForegroundColor = HSSFColor.Teal.Index;
                        style2.FillPattern = FillPattern.SolidForeground;

                        for (int i = destRow.FirstCellNum; i <= destRow.LastCellNum; i++)
                        {
                            if (destRow.GetCell(i) != null)
                                destRow.GetCell(i).CellStyle = style2;
                        }
                    }
                }
            }
        }



    }

    private static void CopyCell(XSSFCell oldCell, HSSFCell newCell, Dictionary styleMap, HSSFWorkbook retVal)
    {
        if (styleMap != null)
        {
            int stHashCode = oldCell.CellStyle.Index;
            XSSFCellStyle sourceCellStyle = null;
            if (styleMap.TryGetValue(stHashCode, out sourceCellStyle)) { }

            HSSFCellStyle destnCellStyle = (HSSFCellStyle)newCell.CellStyle;
            if (sourceCellStyle == null)
            {
                sourceCellStyle = (XSSFCellStyle)oldCell.Sheet.Workbook.CreateCellStyle();
            }
            // destnCellStyle.CloneStyleFrom(oldCell.CellStyle);
            if (!styleMap.Any(p => p.Key == stHashCode))
            {
                styleMap.Add(stHashCode, sourceCellStyle);
            }

            destnCellStyle.VerticalAlignment = VerticalAlignment.Top;
            newCell.CellStyle = (HSSFCellStyle)destnCellStyle;
        }
        switch (oldCell.CellType)
        {
            case CellType.String:
                newCell.SetCellValue(oldCell.StringCellValue);
                break;
            case CellType.Numeric:
                newCell.SetCellValue(oldCell.NumericCellValue);
                break;
            case CellType.Blank:
                newCell.SetCellType(CellType.Blank);
                break;
            case CellType.Boolean:
                newCell.SetCellValue(oldCell.BooleanCellValue);
                break;
            case CellType.Error:
                newCell.SetCellErrorValue(oldCell.ErrorCellValue);
                break;
            case CellType.Formula:
                newCell.SetCellFormula(oldCell.CellFormula);
                break;
            default:
                break;
        }

    }


    private static CellRangeAddress GetMergedRegion(XSSFSheet sheet, int rowNum, short cellNum)
    {
        for (int i = 0; i < sheet.NumMergedRegions; i++)
        {
            CellRangeAddress merged = sheet.GetMergedRegion(i);
            if (merged.IsInRange(rowNum, cellNum))
            {
                return merged;
            }
        }
        return null;
    }

    private static bool IsNewMergedRegion(CellRangeAddress newMergedRegion,
            List mergedRegions)
    {
        return !mergedRegions.Contains(newMergedRegion);
    }
}