public async Task <bool> Auth(string login, string password) { if (login != null && password != null) { LoginResponse loginResponse = await serverWorker.TaskLogin(login, password); if (loginResponse.IsAuthenticationSuccessful) { serverWorker.UserLogin = login; await Navigation.PushAsync(new TabbedUserPage(serverWorker, systemSettings)); } else { await DisplayAlert("Error", "Incorrect login/password pair", "OK"); } } else { await DisplayAlert("Error", "Fields cannot be empty", "OK"); } return(true); }