HttpCookie myCookie = new HttpCookie("ID");
myCookie["ID"] = Aunthicate.ID.ToString();
//myCookie.Expires = DateTime.Now.AddDays(-1d);
System.Web.HttpContext.Current.Response.Cookies.Add(myCookie);
and for get cookies value in session
Session["ID"] = Server.HtmlEncode(Request.Cookies["ID"].Value);