how to save xls file as xlsx file using NPOI c#?

Question

I'm using NPOI to open XLS file, then add some modifications to the XLS file. at the end i want to save it as XLSX file.

i'm using this code to save it as XLS file:

using (var fs = new FileStream(Name, FileMode.Create, FileAccess.Write))
{
     wb.Write(fs);
} 

Is it possible to save this XLS file as XLSX file using NPOI in C#?

Thanks in advance for your response

Answer 1

It is possible in general, but not quite easy, rather it is significantly complicated task.

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 save your file as XLSX after you opened and modified it using NPOI, you need to create new XSSFWorkbook, then for each worksheet of your source file you need to create appropriate XSSFSheet, copy data to it from your original worksheet and so on until you will get full copy of your data, and then save workbook to file.

Answer 2

It's an old question, but I've encountered with the similar problem. This code is using NPOI 2.2.1 from https://npoi.codeplex.com/releases. This code is based on code from Convert xlsx file to xls using NPOI in c# question, but it converts xls->xlsx, not xlsx->xls. Plus it converts styles and fixes bug with ranges. This code works for simple workbooks without charts and other complex stuff.

using NPOI.XSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.SS.Util;
using NPOI.HSSF.UserModel;
using System.Collections.Generic;
using System.Linq;
using System.IO;

namespace XlsToXlsxConverter
{
    public static class XLSToXLSXConverter
    {
        public static byte[] Convert(Stream sourceStream)
        {
            var source = new HSSFWorkbook(sourceStream);
            var destination = new XSSFWorkbook();
            for (int i = 0; i < source.NumberOfSheets; i++)
            {
                var xssfSheet = (XSSFSheet)destination.CreateSheet(source.GetSheetAt(i).SheetName);
                var hssfSheet = (HSSFSheet)source.GetSheetAt(i);
                CopyStyles(hssfSheet, xssfSheet);
                CopySheets(hssfSheet, xssfSheet);
            }
            using (var ms = new MemoryStream())
            {
                destination.Write(ms);
                return ms.ToArray();
            }
        }

        private static void CopyStyles(HSSFSheet from, XSSFSheet to)
        {
            for (short i = 0; i <= from.Workbook.NumberOfFonts; i++)
            {
                CopyFont(to.Workbook.CreateFont(), from.Workbook.GetFontAt(i));
            }

            for (short i = 0; i < from.Workbook.NumCellStyles; i++)
            {
                CopyStyle(to.Workbook.CreateCellStyle(), from.Workbook.GetCellStyleAt(i), to.Workbook, from.Workbook);
            }

        }

        private static void CopyFont(IFont toFront, IFont fontFrom)
        {
            toFront.Boldweight = fontFrom.Boldweight;
            toFront.Charset = fontFrom.Charset;
            toFront.Color = fontFrom.Color;
            toFront.FontHeightInPoints = fontFrom.FontHeightInPoints;            
            toFront.FontName = fontFrom.FontName;           
            toFront.IsBold = fontFrom.IsBold;
            toFront.IsItalic = fontFrom.IsItalic;
            toFront.IsStrikeout = fontFrom.IsStrikeout;
            //toFront.Underline = fontFrom.Underline; <- bug in npoi setter
        }

        private static void CopyStyle(ICellStyle toCellStyle, ICellStyle fromCellStyle, IWorkbook toWorkbook, IWorkbook fromWorkbook)
        {
            toCellStyle.Alignment = fromCellStyle.Alignment;
            toCellStyle.BorderBottom = fromCellStyle.BorderBottom;
            toCellStyle.BorderDiagonal = fromCellStyle.BorderDiagonal;
            toCellStyle.BorderDiagonalColor = fromCellStyle.BorderDiagonalColor;
            toCellStyle.BorderDiagonalLineStyle = fromCellStyle.BorderDiagonalLineStyle;
            toCellStyle.BorderLeft = fromCellStyle.BorderLeft;
            toCellStyle.BorderRight = fromCellStyle.BorderRight;
            toCellStyle.BorderTop = fromCellStyle.BorderTop;
            toCellStyle.BottomBorderColor = fromCellStyle.BottomBorderColor;
            toCellStyle.DataFormat = fromCellStyle.DataFormat;
            toCellStyle.FillBackgroundColor = fromCellStyle.FillBackgroundColor;
            toCellStyle.FillForegroundColor = fromCellStyle.FillForegroundColor;
            toCellStyle.FillPattern = fromCellStyle.FillPattern;
            toCellStyle.Indention = fromCellStyle.Indention;
            toCellStyle.IsHidden = fromCellStyle.IsHidden;
            toCellStyle.IsLocked = fromCellStyle.IsLocked;
            toCellStyle.LeftBorderColor = fromCellStyle.LeftBorderColor;
            toCellStyle.RightBorderColor = fromCellStyle.RightBorderColor;
            toCellStyle.Rotation = fromCellStyle.Rotation;
            toCellStyle.ShrinkToFit = fromCellStyle.ShrinkToFit;
            toCellStyle.TopBorderColor = fromCellStyle.TopBorderColor;
            toCellStyle.VerticalAlignment = fromCellStyle.VerticalAlignment;
            toCellStyle.WrapText = fromCellStyle.WrapText;

            toCellStyle.SetFont(toWorkbook.GetFontAt((short)(fromCellStyle.GetFont(fromWorkbook).Index + 1 )));
        }

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

        private static void CopyRow(HSSFSheet srcSheet, XSSFSheet destSheet, HSSFRow srcRow, XSSFRow destRow, List<CellRangeAddress> mergedRegions)
        {
            destRow.Height = srcRow.Height;

            for (int j = srcRow.FirstCellNum; srcRow.LastCellNum >= 0 && j <= srcRow.LastCellNum; j++)
            {
                var oldCell = (HSSFCell)srcRow.GetCell(j);
                var newCell = (XSSFCell)destRow.GetCell(j);
                if (oldCell != null)
                {
                    if (newCell == null)
                    {
                        newCell = (XSSFCell)destRow.CreateCell(j);
                    }

                    CopyCell(oldCell, newCell);

                    var mergedRegion = GetMergedRegion(srcSheet, srcRow.RowNum,
                            (short)oldCell.ColumnIndex);

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

        private static void CopyCell(HSSFCell oldCell, XSSFCell newCell)
        {
            CopyCellStyle(oldCell, newCell);

            CopyCellValue(oldCell, newCell);
        }

        private static void CopyCellValue(HSSFCell oldCell, XSSFCell newCell)
        {
            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 void CopyCellStyle(HSSFCell oldCell, XSSFCell newCell)
        {
            if (oldCell.CellStyle == null) return;
            newCell.CellStyle = newCell.Sheet.Workbook.GetCellStyleAt((short)(oldCell.CellStyle.Index + 1));


        }

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

        private static bool IsNewMergedRegion(CellRangeAddress newMergedRegion,
                List<CellRangeAddress> mergedRegions)
        {
            return !mergedRegions.Any(r =>
            r.FirstColumn == newMergedRegion.FirstColumn &&
            r.LastColumn == newMergedRegion.LastColumn &&
            r.FirstRow == newMergedRegion.FirstRow &&
            r.LastRow == newMergedRegion.LastRow);
        }
    }
}