弹出模式窗口无法下载文件有关问题

弹出模式窗口无法下载文件问题
A页面弹出模式窗体B
B页面 PageLoad 时从后台读取数据并写成内存流,然后用Response方式下载

C# code

    private void DoExport(byte[] bytes)    {        try        {            var fileName = string.Format("{0}.txt", DateTime.Now.ToString("yyyy.MM.dd_HH.mm.ss"));            Response.ContentType = "application/octet-stream";            Response.AddHeader("Content-Disposition", "attachment; filename="+fileName);            Response.BinaryWrite(bytes);            Response.Flush();            Response.End();        }        catch { }    }