public bool Check(string username, string password)
        {
            StudentWebAPIAsync <User> userApiAsync = new StudentWebAPIAsync <User>(U_url);

            bool log = false;

            foreach (var u in userApiAsync.GetAll())
            {
                if (u.Username.Equals(username) && u.Password.Equals(password))
                {
                    return(true);
                }
                else
                {
                    return(false);
                }
            }
            return(log);
        }
        public bool ReCheck(string username, string password)
        {
            StudentWebAPIAsync <Admin> regApiAsync = new StudentWebAPIAsync <Admin>(_url);

            bool status = false;

            foreach (var r in regApiAsync.GetAll())
            {
                if (r.Username.Equals(username) && r.Password.Equals(password))
                {
                    return(true);
                }
                else
                {
                    return(false);
                }
            }
            return(status);
        }