public void ExportToTxt(Object Sender, EventArgs E)
    {
        //www.flyso.cn www.flyso.cn
        SqlConnection con = new SqlConnection(ConfigurationSettings.AppSettings["sqlcon"]);
        SqlDataAdapter da = new SqlDataAdapter("select distinct mobile_no from [80NT]", con);
        DataSet ds = new DataSet();
        da.Fill(ds, "dtable");
        //生成相应的数据  
        string path = Server.MapPath("80NT.txt");   //根当前程序放在同一个目录  
        if (File.Exists(path))
        {
            File.Delete(path);
        }
        if (!File.Exists(path))
        {
            File.Create(path).Close();
        }
        //生成文本文件的路径  
        FileStream fsobj = new FileStream(path, FileMode.OpenOrCreate, FileAccess.ReadWrite);
        StreamWriter _sw = new StreamWriter(fsobj, System.Text.UnicodeEncoding.Unicode);
        DataTable dt = ds.Tables["dtable"];
        _sw.Write("mobile_no" + "\r\n");
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            _sw.Write(dt.Rows[i]["mobile_no"].ToString().Trim() + "\r\n");
        }
        //循环输出内容以及格式  
        _sw.Close();
        fsobj.Close();
        string contentType = "application/";
        string filename = "flysonet.txt";
        System.Diagnostics.Process.Start("notepad.exe", "80NT.txt");
        HttpContext.Current.Response.Clear();
        HttpContext.Current.Response.Charset = "GB2312";
        HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + filename);
        HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
        HttpContext.Current.Response.ContentType = contentType;
        HttpContext.Current.Response.WriteFile(path);
        HttpContext.Current.Response.End();
        //关闭相应的东东
    }