产生一个免保存在服务器端的流，直接下载

 1StringWriter sw=new StringWriter();
 2            sw.WriteLine("科目名称\t凭证日期\t借方\t贷方");
 3            string s="";
 4            foreach(DataRow dr in Items.Rows)
 5            {
 6                s = dr["AccountName"].ToString();
 7                s += "\t" + Convert.ToDateTime(dr["VouDate"]).ToString("yyyy-MM-dd");
 8                s += "\t" + dr["Debit"].ToString() + "\t" + dr["Credit"].ToString();
 9                sw.WriteLine(s);
10            }
11            sw.Close();
12            Response.Clear();
13            Response.AddHeader("Content-Disposition", "attachment; filename=filename.xls");
14            Response.ContentType = "application/ms-excel            Response.ContentEncoding=System.Text.Encoding.Default;
15            Response.Write(sw);// 把流发送到客户端 
16            Response.End();