在C#中使用NPOI2.0操作Excel2003和Excel2007

Excel2003：

    #region Excel2003
    /// <summary>
    /// 将Excel文件中的数据读出到DataTable中(xls)
    /// </summary>
    /// <param name="file"></param>
    /// <returns></returns>
    public static DataTable ExcelToTableForXLS(string file)
    {
        DataTable dt = new DataTable();
        using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
        {
            XLS.HSSFWorkbook hssfworkbook = new XLS.HSSFWorkbook(fs);
            ISheet sheet = hssfworkbook.GetSheetAt();  

            //表头
            IRow header = sheet.GetRow(sheet.FirstRowNum);
            List<int> columns = new List<int>();
            for (int i = ; i < header.LastCellNum; i++)
            {
                object obj = GetValueTypeForXLS(header.GetCell(i) as XLS.HSSFCell);
                if (obj == null || obj.ToString() == string.Empty)
                {
                    dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                    //continue;
                }
                else
                    dt.Columns.Add(new DataColumn(obj.ToString()));
                columns.Add(i);
            }
            //数据
            for (int i = sheet.FirstRowNum + ; i <= sheet.LastRowNum; i++)
            {
                DataRow dr = dt.NewRow();
                bool hasValue = false;
                foreach (int j in columns)
                {
                    dr[j] = GetValueTypeForXLS(sheet.GetRow(i).GetCell(j) as XLS.HSSFCell);
                    if (dr[j] != null && dr[j].ToString() != string.Empty)
                    {
                        hasValue = true;
                    }
                }
                if (hasValue)
                {
                    dt.Rows.Add(dr);
                }
            }
        }
        return dt;
    }  

    /// <summary>
    /// 将DataTable数据导出到Excel文件中(xls)
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="file"></param>
    public static void TableToExcelForXLS(DataTable dt, string file)
    {
        XLS.HSSFWorkbook hssfworkbook = new XLS.HSSFWorkbook();
        ISheet sheet = hssfworkbook.CreateSheet("Test");  

        //表头
        IRow row = sheet.CreateRow();
        for (int i = ; i < dt.Columns.Count; i++)
        {
            ICell cell = row.CreateCell(i);
            cell.SetCellValue(dt.Columns[i].ColumnName);
        }  

        //数据
        for (int i = ; i < dt.Rows.Count; i++)
        {
            IRow row1 = sheet.CreateRow(i + );
            for (int j = ; j < dt.Columns.Count; j++)
            {
                ICell cell = row1.CreateCell(j);
                cell.SetCellValue(dt.Rows[i][j].ToString());
            }
        }  

        //转为字节数组
        MemoryStream stream = new MemoryStream();
        hssfworkbook.Write(stream);
        var buf = stream.ToArray();  

        //保存为Excel文件
        using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))
        {
            fs.Write(buf, , buf.Length);
            fs.Flush();
        }
    }  

    /// <summary>
    /// 获取单元格类型(xls)
    /// </summary>
    /// <param name="cell"></param>
    /// <returns></returns>
    private static object GetValueTypeForXLS(XLS.HSSFCell cell)
    {
        if (cell == null)
            return null;
        switch (cell.CellType)
        {
            case CellType.BLANK: //BLANK:
                return null;
            case CellType.BOOLEAN: //BOOLEAN:
                return cell.BooleanCellValue;
            case CellType.NUMERIC: //NUMERIC:
                return cell.NumericCellValue;
            case CellType.STRING: //STRING:
                return cell.StringCellValue;
            case CellType.ERROR: //ERROR:
                return cell.ErrorCellValue;
            case CellType.FORMULA: //FORMULA:
            default:
                return "=" + cell.CellFormula;
        }
    }
    #endregion  

Excel2007：

    #region Excel2007
    /// <summary>
    /// 将Excel文件中的数据读出到DataTable中(xlsx)
    /// </summary>
    /// <param name="file"></param>
    /// <returns></returns>
    public static DataTable ExcelToTableForXLSX(string file)
    {
        DataTable dt = new DataTable();
        using (FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read))
        {
            XSSFWorkbook xssfworkbook = new XSSFWorkbook(fs);
            ISheet sheet = xssfworkbook.GetSheetAt();  

            //表头
            IRow header = sheet.GetRow(sheet.FirstRowNum);
            List<int> columns = new List<int>();
            for (int i = ; i < header.LastCellNum; i++)
            {
                object obj = GetValueTypeForXLSX(header.GetCell(i) as XSSFCell);
                if (obj == null || obj.ToString() == string.Empty)
                {
                    dt.Columns.Add(new DataColumn("Columns" + i.ToString()));
                    //continue;
                }
                else
                    dt.Columns.Add(new DataColumn(obj.ToString()));
                columns.Add(i);
            }
            //数据
            for (int i = sheet.FirstRowNum + ; i <= sheet.LastRowNum; i++)
            {
                DataRow dr = dt.NewRow();
                bool hasValue = false;
                foreach (int j in columns)
                {
                    dr[j] = GetValueTypeForXLSX(sheet.GetRow(i).GetCell(j) as XSSFCell);
                    if (dr[j] != null && dr[j].ToString() != string.Empty)
                    {
                        hasValue = true;
                    }
                }
                if (hasValue)
                {
                    dt.Rows.Add(dr);
                }
            }
        }
        return dt;
    }  

    /// <summary>
    /// 将DataTable数据导出到Excel文件中(xlsx)
    /// </summary>
    /// <param name="dt"></param>
    /// <param name="file"></param>
    public static void TableToExcelForXLSX(DataTable dt, string file)
    {
        XSSFWorkbook xssfworkbook = new XSSFWorkbook();
        ISheet sheet = xssfworkbook.CreateSheet("Test");  

        //表头
        IRow row = sheet.CreateRow();
        for (int i = ; i < dt.Columns.Count; i++)
        {
            ICell cell = row.CreateCell(i);
            cell.SetCellValue(dt.Columns[i].ColumnName);
        }  

        //数据
        for (int i = ; i < dt.Rows.Count; i++)
        {
            IRow row1 = sheet.CreateRow(i + );
            for (int j = ; j < dt.Columns.Count; j++)
            {
                ICell cell = row1.CreateCell(j);
                cell.SetCellValue(dt.Rows[i][j].ToString());
            }
        }  

        //转为字节数组
        MemoryStream stream = new MemoryStream();
        xssfworkbook.Write(stream);
        var buf = stream.ToArray();  

        //保存为Excel文件
        using (FileStream fs = new FileStream(file, FileMode.Create, FileAccess.Write))
        {
            fs.Write(buf, , buf.Length);
            fs.Flush();
        }
    }  

    /// <summary>
    /// 获取单元格类型(xlsx)
    /// </summary>
    /// <param name="cell"></param>
    /// <returns></returns>
    private static object GetValueTypeForXLSX(XSSFCell cell)
    {
        if (cell == null)
            return null;
        switch (cell.CellType)
        {
            case CellType.BLANK: //BLANK:
                return null;
            case CellType.BOOLEAN: //BOOLEAN:
                return cell.BooleanCellValue;
            case CellType.NUMERIC: //NUMERIC:
                return cell.NumericCellValue;
            case CellType.STRING: //STRING:
                return cell.StringCellValue;
            case CellType.ERROR: //ERROR:
                return cell.ErrorCellValue;
            case CellType.FORMULA: //FORMULA:
            default:
                return "=" + cell.CellFormula;
        }
    }  

注意：操作Excel2003与操作Excel2007使用的是不同的命名空间下的内容

使用NPOI.HSSF.UserModel空间下的HSSFWorkbook操作Excel2003

使用NPOI.XSSF.UserModel空间下的XSSFWorkbook操作Excel2007

        /// <summary>
        /// 写入到文件  IWorkbook 接口实现
        /// </summary>
        /// <param name="book"></param>
        /// <param name="fileName"></param>
        /// <returns></returns>
        private bool WriteToFile(IWorkbook book, string fileName)
        {
            bool result = true;
            try
            {
                using (MemoryStream ms = new MemoryStream())
                {
                    string filePath = Path.GetDirectoryName(fileName);
                    if (!Directory.Exists(filePath))
                    {
                        Directory.CreateDirectory(filePath);
                    }
                    book.Write(ms);
                    //保存为Excel文件
                    var buf = ms.ToArray();
                    using (FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write))
                    {
                        fs.Write(buf, , buf.Length);
                        fs.Flush();
                    }
                }
            }
            catch (Exception e)
            {
                LogHelper.WriteErrorLog(e.Message, e);
                result = false;
            }
            finally
            {
                GC.Collect();
            }
            return result;
        }