public static void CreateExcel(DataSet ds)         {             string filename = DateTime.Now.ToString("yyyyMMddHHmmssff") + ".xls";             HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("GB2312");             HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + filename);             string colHeaders = "", ls_item = "";             //定义表对象与行对象，同时用DataSet对其值进行初始化             DataTable dt = ds.Tables[0];             DataRow[] myRow = dt.Select();//可以类似dt.Select("id>10")之形式达到数据筛选目的             int i = 0;             int cl = dt.Columns.Count;             //取得数据表各列标题，各标题之间以\t分割，最后一个列标题后加回车符             for (i = 0; i < cl; i++)             {                 if (i == (cl - 1))//最后一列，加\n                 {                     colHeaders += dt.Columns[i].Caption.ToString() + "\n";                 }                 else                 {                     colHeaders += dt.Columns[i].Caption.ToString() + "\t";                 }             }             HttpContext.Current.Response.Write(colHeaders);             //向HTTP输出流中写入取得的数据信息             //逐行处理数据              foreach (DataRow row in myRow)             {                 //当前行数据写入HTTP输出流，并且置空ls_item以便下行数据                    for (i = 0; i < cl; i++)                 {                     if (i == (cl - 1))//最后一列，加\n                     {                         ls_item += row[i].ToString() + "\n";                     }                     else                     {                         ls_item += row[i].ToString() + "\t";                     }                 }                 HttpContext.Current.Response.Write(ls_item);                 ls_item = "";             }             HttpContext.Current.Response.End();         }