写入到Excel表格文件当中，导出/导入数据

    /// <summary>
        /// 写入到Excel表格文件当中，导出数据
        /// </summary>
        /// <param name="dt"></param>
        /// <returns></returns>
        public bool DataTableToExcel(DataTable dt, string DataFile)
        {
            bool result = false;
            IWorkbook workbook = null;
            FileStream fs = null;
            IRow row = null;
            ISheet sheet = null;
            ICell cell = null;
            try
            {
                if (dt != null && dt.Rows.Count > 0)
                {
                    workbook = new HSSFWorkbook();
                    string NowBOPName = this.CmbBOPName.Text.Trim();
                    sheet = workbook.CreateSheet(NowBOPName);//创建一个名称为Sheet0的表
                    int rowCount = dt.Rows.Count;//行数
                    int columnCount = dt.Columns.Count;//列数  

                    //把A0:C0合并为一个单元格 并赋值
                    ICell hbcell = sheet.CreateRow(0).CreateCell(0);
                    hbcell.SetCellValue(NowBOPName + "工序");
                    sheet.AddMergedRegion(new NPOI.SS.Util.CellRangeAddress(0, 0, 0, 2));

                    //设置样式 居中 字体
                    ICellStyle hbstyle = workbook.CreateCellStyle();
                    hbstyle.VerticalAlignment = VerticalAlignment.Center;
                    hbstyle.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;
                    IFont hbfont = workbook.CreateFont();
                    hbfont.FontHeight = 15 * 20;
                    hbstyle.SetFont(hbfont);
                    hbcell.CellStyle = hbstyle;

                    //设置列头
                    row = sheet.CreateRow(1);//excel第一行设为标题，第二行列头
                    for (int c = 0; c < columnCount; c++)
                    {
                        cell = row.CreateCell(c);
                        cell.SetCellValue(dt.Columns[c].ColumnName);
                    }

                    //设置每行每列的单元格,
                    for (int i = 0; i < rowCount; i++)
                    {
                        row = sheet.CreateRow(i + 2);//excel第三行开始写入数据
                        for (int j = 0; j < columnCount; j++)
                        {
                            cell = row.CreateCell(j);
                            cell.SetCellValue(dt.Rows[i][j].ToString());
                        }
                    }
                    using (fs = File.OpenWrite(DataFile))
                    {
                        workbook.Write(fs);//向打开的这个xls文件中写入数据
                        result = true;
                    }
                }
                return result;
            }
            catch (Exception ex)
            {
                if (fs != null)
                {
                    fs.Close();
                }
                return false;
            }
        }

   /// <summary>
        /// 将excel导入到datatable
        /// </summary>
        /// <param name="filePath">excel路径</param>
        /// <param name="isColumnName">第一行是否是列名</param>
        /// <returns>返回datatable</returns>
        public static DataTable ExcelToDataTable(string filePath, bool isColumnName)
        {
            DataTable dataTable = null;
            FileStream fs = null;
            DataColumn column = null;
            DataRow dataRow = null;
            IWorkbook workbook = null;
            ISheet sheet = null;
            IRow row = null;
            ICell cell = null;
            int startRow = 0;
            try
            {
                using (fs = File.OpenRead(filePath))
                {
                    // 2007版本
                    if (filePath.IndexOf(".xlsx") > 0)
                        workbook = new XSSFWorkbook(fs);
                    // 2003版本
                    else if (filePath.IndexOf(".xls") > 0)
                        workbook = new HSSFWorkbook(fs);

                    if (workbook != null)
                    {

                        sheet = workbook.GetSheetAt(0);//读取第一个sheet，当然也可以循环读取每个sheet

                        dataTable = new DataTable();
                        if (sheet != null)
                        {
                            int rowCount = sheet.LastRowNum;//总行数
                            if (rowCount > 0)
                            {
                                IRow firstRow = sheet.GetRow(1);//第二行列名
                                int cellCount = firstRow.LastCellNum;//列数

                                //构建datatable的列
                                if (isColumnName)
                                {
                                    startRow = 2;//如果第一行是标题，第二行列名，则从第二行开始读取
                                    for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                                    {
                                        cell = firstRow.GetCell(i);
                                        if (cell != null)
                                        {
                                            if (cell.StringCellValue != null)
                                            {
                                                column = new DataColumn(cell.StringCellValue);
                                                dataTable.Columns.Add(column);
                                            }
                                        }
                                    }
                                }
                                else
                                {
                                    for (int i = firstRow.FirstCellNum; i < cellCount; ++i)
                                    {
                                        column = new DataColumn("column" + (i + 1));
                                        dataTable.Columns.Add(column);
                                    }
                                }

                                //填充行
                                for (int i = startRow; i <= rowCount; ++i)
                                {
                                    row = sheet.GetRow(i);
                                    if (row == null) continue;

                                    dataRow = dataTable.NewRow();
                                    for (int j = row.FirstCellNum; j < cellCount; ++j)//dataTable.Columns.Count
                                    {
                                        cell = row.GetCell(j);
                                        if (cell == null)
                                        {
                                            dataRow[j] = "";
                                        }
                                        else
                                        {
                                            //CellType(Unknown = -1,Numeric = 0,String = 1,Formula = 2,Blank = 3,Boolean = 4,Error = 5,)
                                            switch (cell.CellType)
                                            {
                                                case CellType.Blank:
                                                    dataRow[j - row.FirstCellNum] = "";
                                                    break;
                                                case CellType.Numeric:
                                                    short format = cell.CellStyle.DataFormat;
                                                    //对时间格式（2015.12.5、2015/12/5、2015-12-5等）的处理
                                                    if (format == 14 || format == 31 || format == 57 || format == 58)
                                                        dataRow[j - row.FirstCellNum] = cell.DateCellValue;
                                                    else
                                                        dataRow[j - row.FirstCellNum] = cell.NumericCellValue;
                                                    break;
                                                case CellType.String:
                                                    dataRow[j - row.FirstCellNum] = cell.StringCellValue;
                                                    break;
                                                case CellType.Formula:
                                                    //System.Globalization.NumberFormatInfo nfi = new System.Globalization.NumberFormatInfo();
                                                    //nfi.NumberDecimalDigits = 2;
                                                    //short format = cell.CellStyle.Format("{0:F2}", Convert.ToDouble(23, 5235);
                                                    dataRow[j - row.FirstCellNum] = ((float)cell.NumericCellValue);
                                                    break;
                                            }
                                        }
                                    }
                                    dataTable.Rows.Add(dataRow);
                                }
                            }
                        }
                    }
                }
                return dataTable;
            }
            catch (Exception ex)
            {

                if (fs != null)
                {
                    fs.Close();
                }
                return null;
            }
        }