public static   class ExportExcel

    {

        public static void DataTable2Excel(string attachName, DataTable tab)

        {

            string file = HttpContext.Current.Server.MapPath("/uploads/export/" + Guid.NewGuid().ToString() + ".xls");

            Workbook workbook = new Workbook();

            Worksheet worksheet = new Worksheet("Sheet1");

            //构建表头

            for (int col = 0; col < tab.Columns.Count; col++)

            {

                worksheet.Cells[0, col] = new Cell(tab.Columns[col].ColumnName);

            }

            for (int rowIndex = 0; rowIndex < tab.Rows.Count; rowIndex++)

            {

                for (int colIndex = 0; colIndex < tab.Columns.Count; colIndex++)

                {

                    worksheet.Cells[rowIndex + 1, colIndex] = new Cell(tab.Rows[rowIndex][colIndex].ToString());

                }

            }

            //设置默认宽度

            if (worksheet.Cells.LastRowIndex > 1)

            {

                for (int n = 0; n < tab.Columns.Count; n++)

                {

                    if (worksheet.Cells[1, n].Value.ToString().Length >= 50)

                        worksheet.Cells.ColumnWidth[(ushort)n] = 10000;

                    else if (worksheet.Cells[1, n].Value.ToString().Length >= 10)

                        worksheet.Cells.ColumnWidth[(ushort)n] = (ushort)(worksheet.Cells[1, n].Value.ToString().Length * 300);

                    else

                        worksheet.Cells.ColumnWidth[(ushort)n] = 3000;

                }

            }

            else

                worksheet.Cells.ColumnWidth[0, (ushort)(tab.Columns.Count - 1)] = 3000;

            workbook.Worksheets.Add(worksheet);

            workbook.Save(file);

            FileInfo info = new FileInfo(file);

            long size = 0;

            if (info.Exists)

                size = info.Length;

            HttpContext.Current.Response.AddHeader("content-type", "application/x-msdownload;");

            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(attachName + ".xls"));

            HttpContext.Current.Response.AddHeader("content-length", size.ToString());

            HttpContext.Current.Response.WriteFile(file, 0, size);

        }

    }