关于NPOIExcel导出excel

1.支持导出多个sheet文件

 /// <summary>
        ///  导出到Excel并下载（html）
        /// </summary>
        /// <param name="tablels">需要导出的Excel表集合</param>
        public static void ToExcel(List<DataTable> tablels, string fileName = "")
        {

            if (fileName == "")
            {
                fileName = "数据导出汇总-" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + ".xls"; // 文件名称
            }
            string urlPath = "UpFiles/ExcelFiles/" + fileName; // 文件下载的URL地址，供给前台下载

            string filePath = HttpContext.Current.Server.MapPath("\" + urlPath); // 文件路径

            string directoryName = Path.GetDirectoryName(filePath);

            if (!Directory.Exists(directoryName))
            {
                Directory.CreateDirectory(directoryName);
            }
            IWorkbook workBook = new HSSFWorkbook();

            foreach (DataTable table in tablels)
            {

                string sheetName = table.TableName;
                FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
                sheetName = string.IsNullOrEmpty(sheetName) ? "sheet1" : sheetName;
                ISheet sheet = workBook.CreateSheet(sheetName);

                //处理表格标题
                IRow row = sheet.CreateRow(0);
                row.CreateCell(0).SetCellValue(sheetName);
                sheet.AddMergedRegion(new CellRangeAddress(0, 0, 0, table.Columns.Count - 1));
                row.Height = 500;

                ICellStyle cellStyle = workBook.CreateCellStyle();
                IFont font = workBook.CreateFont();
                font.FontName = "微软雅黑";
                font.FontHeightInPoints = 17;
                cellStyle.SetFont(font);
                cellStyle.VerticalAlignment = VerticalAlignment.Center;
                cellStyle.Alignment = HorizontalAlignment.Center;
                row.Cells[0].CellStyle = cellStyle;

                //处理表格列头
                row = sheet.CreateRow(1);
                for (int i = 0; i < table.Columns.Count; i++)
                {
                    row.CreateCell(i).SetCellValue(table.Columns[i].ColumnName);
                    row.Height = 350;
                    sheet.AutoSizeColumn(i);
                }

                //处理数据内容
                for (int i = 0; i < table.Rows.Count; i++)
                {
                    row = sheet.CreateRow(2 + i);
                    row.Height = 250;
                    for (int j = 0; j < table.Columns.Count; j++)
                    {
                        row.CreateCell(j).SetCellValue(table.Rows[i][j].ToString());
                        sheet.SetColumnWidth(j, 256 * 15);
                    }
                }
                //写入数据流
                workBook.Write(fs);
                fs.Flush();
                fs.Close();
            }
            // 3.进行Excel转换操作，并返回转换的文件下载链接 
            System.Web.Script.Serialization.JavaScriptSerializer js = new System.Web.Script.Serialization.JavaScriptSerializer();
            HttpContext.Current.Response.ContentType = "text/plain";
            HttpContext.Current.Response.Write(js.Serialize(urlPath)); // 返回Json格式的内容   
        }

2.只支持一个sheet文件

 /// <summary>
        ///  导出到Excel并下载（html）
       /// </summary>
       /// <param name="table">数据源</param>
       /// <param name="title">标题</param>
       /// <param name="sheetName">sheetName名称</param>
       /// <param name="fileName">路径</param>
        public static void ToExcel(DataTable table, string title, string sheetName, string fileName = "")
        {
            if (fileName == "")
            {
                fileName = sheetName + "-" + DateTime.Now.ToString("yyyyMMddHHmmssfff") + ".xls"; // 文件名称
            }
            string urlPath = "UpFiles/ExcelFiles/" + fileName; // 文件下载的URL地址，供给前台下载

            string filePath = HttpContext.Current.Server.MapPath("\" + urlPath); // 文件路径

            string directoryName = Path.GetDirectoryName(filePath);

            if (!Directory.Exists(directoryName))
            {
                Directory.CreateDirectory(directoryName);
            }

            FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite);
            IWorkbook workBook = new HSSFWorkbook();
            sheetName = string.IsNullOrEmpty(sheetName) ? "sheet1" : sheetName;
            ISheet sheet = workBook.CreateSheet(sheetName);

            //处理表格标题
            IRow row = sheet.CreateRow(0);
            row.CreateCell(0).SetCellValue(title);
            sheet.AddMergedRegion(new CellRangeAddress(0, 0, 0, table.Columns.Count - 1));
            row.Height = 500;

            ICellStyle cellStyle = workBook.CreateCellStyle();
            IFont font = workBook.CreateFont();
            font.FontName = "微软雅黑";
            font.FontHeightInPoints = 17;
            cellStyle.SetFont(font);
            cellStyle.VerticalAlignment = VerticalAlignment.Center;
            cellStyle.Alignment = HorizontalAlignment.Center;
            row.Cells[0].CellStyle = cellStyle;

            //处理表格列头
            row = sheet.CreateRow(1);
            for (int i = 0; i < table.Columns.Count; i++)
            {
                row.CreateCell(i).SetCellValue(table.Columns[i].ColumnName);
                row.Height = 350;
                sheet.AutoSizeColumn(i);
            }

            //处理数据内容
            for (int i = 0; i < table.Rows.Count; i++)
            {
                row = sheet.CreateRow(2 + i);
                row.Height = 250;
                for (int j = 0; j < table.Columns.Count; j++)
                {
                    row.CreateCell(j).SetCellValue(table.Rows[i][j].ToString());
                    sheet.SetColumnWidth(j, 256 * 15);
                }
            }

            //写入数据流
            workBook.Write(fs);
            fs.Flush();
            fs.Close();

            // 3.进行Excel转换操作，并返回转换的文件下载链接 
            System.Web.Script.Serialization.JavaScriptSerializer js = new System.Web.Script.Serialization.JavaScriptSerializer();
            HttpContext.Current.Response.ContentType = "text/plain";
            HttpContext.Current.Response.Write(js.Serialize(urlPath)); // 返回Json格式的内容  
        }