HSSFWorkbook hssfworkbook;

        ISheet sheet1;

        public void BuildExcel()

        {

            hssfworkbook = new HSSFWorkbook();

            // 新建一个Excel页签

            sheet1 = hssfworkbook.CreateSheet("Sheet1");

            // 创建新增行

            for (var i = 0; i < 10;i++ )

            {

                IRow row1 = sheet1.CreateRow(i);

                for (var j = 0; j < 10; j++)

                {

                    //新建单元格

                    ICell cell = row1.CreateCell(j);

                    // 单元格赋值

                    cell.SetCellValue("单元格"+j.ToString());

                }

            }

            // 设置行宽度

            sheet1.SetColumnWidth(2, 10 * 256);

            // 获取单元格 并设置样式

            ICellStyle styleCell = hssfworkbook.CreateCellStyle();

            //居中

            styleCell.Alignment = NPOI.SS.UserModel.HorizontalAlignment.Center;

            //垂直居中

            styleCell.VerticalAlignment = VerticalAlignment.Top;

            ICellStyle cellStyle = hssfworkbook.CreateCellStyle();

            //设置字体

            IFont fontColorRed = hssfworkbook.CreateFont();

            fontColorRed.Color = HSSFColor.OliveGreen.Red.Index;

            styleCell.SetFont(fontColorRed);

            sheet1.GetRow(2).GetCell(2).CellStyle = styleCell;

            // 合并单元格

            sheet1.AddMergedRegion(new CellRangeAddress(2, 4, 2, 5));

            // 输出Excel

            string filename = "cnblogs.rhythmk.com.导出.xls";

            var context = HttpContext.Current;

            context.Response.ContentType = "application/vnd.ms-excel";

            context.Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}", context.Server.UrlEncode(filename)));

            context.Response.Clear();

            MemoryStream file = new MemoryStream();

            hssfworkbook.Write(file);

            context.Response.BinaryWrite(file.GetBuffer());

            context.Response.End();

        }