async void navigateToMainPage(object sender, System.EventArgs e) { List <User> allUsers = await service.GetAllUsers(); bool userFound = false; foreach (User user in allUsers) { if (username.Text == user.username && password.Text == user.password) { Console.WriteLine("Found User"); User loggedUser = user; userFound = true; await Navigation.PushAsync(new MainPage(loggedUser.id)); break; } } if (!userFound) { await DisplayAlert("Invalid Credentials", "Please enter valid credentials", "OK"); } }