Response.Clear();
  Response.ClearContent();
  Response.ClearHeaders();
  Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
  Response.AddHeader("Content-Length", fileInfo.Length);
  Response.AddHeader("Content-Transfer-Encoding", "binary");
  Response.ContentType = "application/octet-stream";
  Response.WriteFile(fileInfo.FullName);
  Response.Flush();
  Response.End();