private async void OnConfirmButtonClicked(object sender, System.EventArgs e)
        {
            if (string.IsNullOrWhiteSpace(Entry_Password.Text))
            {
                await DisplayAlert(null, "Please enter a password", "OK");

                return;
            }

            int newId = await Communications.Register(Entry_Username.Text,
                                                      Entry_Password.Text, avatarNum);

            if (newId > 0)
            {
                await DisplayAlert("Register success!", "Your id number is " + newId +
                                   ". Please remember this as this will be used as your login",
                                   "ok");
            }
            else
            {
                await DisplayAlert("Register failed!", "Please try again", "ok");
            }
        }