All types(pdf,excel,word,txt..etc) of Document viewer in asp.net

var fileInfo = new FileInfo(fileFullName);
            string fileName = Path.GetFileName(fileFullName);
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + fileName);
            HttpContext.Current.Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            HttpContext.Current.Response.ContentType = "application/octet-stream";
            HttpContext.Current.Response.Flush();
            HttpContext.Current.Response.WriteFile(fileFullName);
            HttpContext.Current.Response.End();
}