// GET: Profile/ShowUser
        public ActionResult ShowUser()
        {
            if (string.IsNullOrEmpty(Request.QueryString["username"]))
            {
                return(Redirect("/Profile"));
            }

            UserHandle handle = UserManager.Default.QueryUserByName(Request.QueryString["username"]);

            if (handle == null)
            {
                // 用户不存在。
                return(Redirect("/Profile"));
            }

            UserProfileModel model = UserProfileModel.FromUserHandle(handle);

            return(View(model));
        }