将数据导出至Excel（标准Excel）

       private static Stream ExportDataTableToExcel(DataTable sourceTable, string sheetName)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            MemoryStream ms = new MemoryStream();
            ISheet sheet = workbook.CreateSheet(sheetName);
            IRow headerRow = sheet.CreateRow(0);
            // handling header.
            foreach (DataColumn column in sourceTable.Columns)
                headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);

            // handling value.
            int rowIndex = 1;

            foreach (DataRow row in sourceTable.Rows)
            {
                IRow dataRow = sheet.CreateRow(rowIndex);

                foreach (DataColumn column in sourceTable.Columns)
                {
                    dataRow.CreateCell(column.Ordinal).SetCellValue(row[column].ToString());
                }

                rowIndex++;
            }

            workbook.Write(ms);
            ms.Flush();
            ms.Position = 0;

            sheet = null;
            headerRow = null;
            workbook = null;

            return ms;
        }
        /// <summary>
        /// 由DataTable导出Excel
        /// </summary>
        /// <param name="sourceTable">要导出数据的DataTable</param>
        /// <param name="fileName">指定Excel工作表名称</param>
        /// <returns>Excel工作表</returns>
        public static void ExportDataTableToExcel(DataTable sourceTable, string fileName, string sheetName)
        {
            MemoryStream ms = ExportDataTableToExcel(sourceTable, sheetName) as MemoryStream;
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");
            HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + fileName);
            HttpContext.Current.Response.BinaryWrite(ms.ToArray());
            HttpContext.Current.Response.End();
            ms.Close();
            ms = null;
        }