private void ViewDocument(int attachment_id, HttpContext context)
{
var mail_box_manager = new MailBoxManager(ConfigurationManager.ConnectionStrings["mail"], 0);
var file = mail_box_manager.GetMessageAttachment(attachment_id, TenantId, Username);
var temp_file_url = file.GerPreSignedUrl();
var viewer_url = CommonLinkUtility.GetFileWebViewerExternalUrl(temp_file_url, file.fileName);
viewer_url = new UriBuilder(CommonLinkUtility.GetFullAbsolutePath(viewer_url)).ToString();
context.Response.Redirect(viewer_url, false);
}