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 package. Please let me know how we can achieve it in NPOI with c#.

Thanks in advance.

Answer 1

This is my suggest :

• Use this library to read excel files in format 2007 https://excelpackage.codeplex.com/

• Use this library to save file as format 2003 https://code.google.com/p/excellibrary/

Answer 2

It is possible in general, but not quite easy.

XLS file format is handled by HSSFWorkbook class (and according HSSFSheet and so on). XLSX file format is handled by XSSFWorkbook class (and XSSFSheet and so on).

So in order to convert your file from XLSX to XLS you need to:

• create XSSFWorkbook, load data to it from file;
• create new HSSFWorkbook;
• for each worksheet in original file create HSSFSheet and copy all the data from original worksheet to this new one
• write your HSSFWorkbook to file.

So there is a lot of work to be done here, and this is significantly complicated task.

Probably NPOI is not the best solution in your case.

Answer 3

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<int, XSSFCellStyle> styleMap = new Dictionary<int, XSSFCellStyle>();
        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<int, XSSFCellStyle> styleMap, HSSFWorkbook retVal)
    {
        // manage a list of merged zone in order to not insert two times a
        // merged zone
        List<CellRangeAddress> mergedRegions = new List<CellRangeAddress>();
        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<int, XSSFCellStyle> 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<CellRangeAddress> mergedRegions)
    {
        return !mergedRegions.Contains(newMergedRegion);
    }
}