protected void btn3_Click(object sender, EventArgs e)      {          string sel = "select EX_Parent ,EX_PostCode ,EX_Address  from EnterInfo where EX_Mark like '%" + txtMark3.Text.Trim() + "%'";          DataTable dt = sqlHelper.ExectueTable(sel);  //取datatable

rtInfo.DataSource = dt;  rtInfo.DataBind();  rtInfo.Visible = true;  string str = "";    for (int i = 0; i < this.rtInfo.Items.Count; i++)  {      Label labName = (Label)rtInfo.Items[i].FindControl("labName");      Label labCode = (Label)rtInfo.Items[i].FindControl("labCode");      Label labAddress = (Label)rtInfo.Items[i].FindControl("labAddress");        string vv = labName.Text;      str = str + (vv + ",");      string vv1 = labCode.Text;      str = str + (vv1 + ",");      string vv2 = labAddress.Text;      str = str + vv2;      str = str + ("\r\n");  }    Response.Clear();  Response.Buffer = true;  Response.Charset = "GB2312";  Response.ContentEncoding = System.Text.Encoding.UTF8;  //string val="online;filename=消费明细"+string.Format("{0:yyyyMMddHHmmss}",System.DateTime.Now)+".txt";  Response.AddHeader("Content-Disposition", "attachment;filename=" + Server.UrlEncode("消费明细" + string.Format("{0:yyyyMMddHHmmss}", System.DateTime.Now) + ".txt"));  //指定返回的是一个不能被客户端读取的流，必须被下载     Response.ContentType = "text/plain";  //把文件流发送到客户端     Response.Write(str.ToString());  //停止页面的执行     Response.End();