设置：
HttpCookie cookie = new HttpCookie("cookieName"); cookie.Value = "name1" HttpContext.Current.Response.Cookies.Add(cookie);
读取：
HttpContext.Current.Request.Cookies["cookieName"].Value
判断cookie是否存在：
if(HttpContext.Current.Request.Cookies["cookieName"]==null){ //do something }
设置cookie有效期
15383239821
cookie.Expires = DateTime.Now.AddDays(1);
