private async void doLogin(string studentID, string password) { //loading LoadingOverlay.Instance.showLoading(this); StudentList studentList = new StudentList(); bool loginStatus = await studentList.login(studentID, password); if (loginStatus) { //Get student profile from api LoadingOverlay.Instance.showLoading(this); Student std = await studentList.getById(studentID); if (std != null) { AppParam.Instance.student = std; this.showNext(); } else { //show register screen this.doRegistration(studentID); } this.showNext(); } else { AppParam.Instance.showAlertMessage("Login Status", "Student ID and Password are not match!"); } }