(转)导出EXCEL时科学计数法问题

//1）  文本：vnd.ms-excel.numberformat:@
//2）  日期：vnd.ms-excel.numberformat:yyyy/mm/dd
//3）  数字：vnd.ms-excel.numberformat:#,##0.00
//4）  货币：vnd.ms-excel.numberformat:￥#,##0.00
//5）  百分比：vnd.ms-excel.numberformat: #0.00%

HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.Charset = "";
            HttpContext.Current.Response.ContentType = "application/vnd.ms-xls";
            HttpContext.Current.Response.AddHeader("content-disposition", "attachment;filename=" + HttpUtility.UrlEncode(excelname + ".xls"));
            StringBuilder table = new StringBuilder();
            DataTable dt = ds.Tables[0];
            table.Append("<table style='border:1px solid #000000'><tr>");
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                table.Append("<td>");
                table.Append(dt.Columns[i].Caption.ToString()); //标格的标题
                table.Append("</td>");
            }
            table.Append("</tr>");
            for (int i = 0; i < dt.Rows.Count; i++)
            {
                table.Append("<tr>");
                for (int j = 0; j < dt.Columns.Count; j++)
                {
                    table.Append("<td style='vnd.ms-excel.numberformat:@'>");
                    table.Append(dt.Rows[i][j].ToString());
                    table.Append("</td>");
                }
                table.Append("</tr>");
            }
            table.Append("</table>");
            return table.ToString();
            HttpContext.Current.Response.Write(table);
            HttpContext.Current.Response.End();