第一种模式：同一顶级域名下cookie共享，代码如下
HttpCookie cookies = new HttpCookie("Token");
cookies.Expires = DateTime.Now.AddDays(7);
cookies.Path = "/";
cookies.Domain = "xxxx.com";//设置同一顶级域名
cookies.Value = "token的值";
System.Web.HttpContext.Current.Response.Cookies.Add(cookies);
第二种模式：跨域下实现单点登录