export Excel to DataTable using NPOI

Question

I want to read Excel Tables 2010 xlsx using NPOI and then export data to DataTables but don\'t know how to use it. Can anyone show me step by step how to export Excel to Datatab

Answer 1

Base on @Sean 's GREAT Answer and example of NPOI, I write the mothod to Convert all worksheets in xls file to DataSet and Convert DataSet back to xls file :

    public static DataSet GetDataSetFromXls(string excelFilePath)
    {
        IWorkbook workbook;
        using (FileStream stream = new FileStream(excelFilePath, FileMode.Open, FileAccess.Read))
        {
            workbook = new HSSFWorkbook(stream);  //2003 xls
            //workbook = new XSSFWorkbook();  //2007 xlsx
        }

        DataSet ds = new DataSet();
        for (int i = 0; i < workbook.NumberOfSheets; i++)
        {
            ISheet sheet = workbook.GetSheetAt(i); // zero-based index of your target sheet
            DataTable dt = new DataTable(sheet.SheetName);

            // write header row
            IRow headerRow = sheet.GetRow(0);
            foreach (ICell headerCell in headerRow)
            {
                dt.Columns.Add(headerCell.ToString());
            }

            // write the rest
            int rowIndex = 0;
            foreach (IRow row in sheet)
            {
                // skip header row
                if (rowIndex++ == 0) continue;
                DataRow dataRow = dt.NewRow();
                dataRow.ItemArray = row.Cells.Select(c => c.ToString()).ToArray();
                dt.Rows.Add(dataRow);
            }

            ds.Tables.Add(dt);
        }

        return ds;
    }


    public static void SaveDataSetToXls(DataSet ds, string savedExcelFilePath)
    {
        //IWorkbook workbook = new XSSFWorkbook();
        IWorkbook workbook = new HSSFWorkbook();

        foreach (DataTable dt in ds.Tables)
        {
            ISheet sheet = workbook.CreateSheet(dt.TableName);

            var row0 = sheet.CreateRow(0);//header
            for (int j = 0; j < dt.Columns.Count; j++)
            {
                row0.CreateCell(j).SetCellValue(dt.Columns[j].ColumnName);
            }

            for (int i = 0; i < dt.Rows.Count; i++)//rest
            {
                var row = sheet.CreateRow(1+i);
                for (int j = 0; j < dt.Columns.Count; j++)
                    row.CreateCell(j).SetCellValue(dt.Rows[i][j].ToString());
            }
        }

        FileStream sw = File.Create(savedExcelFilePath);
        workbook.Write(sw);
        sw.Close();
    }