void _btnNext_Click(object sender, EventArgs e)
        {
            if (viewModel.CurrentQuestion.WasAnswered)
            {
                _ClearListItems();

                if (_btnNext.Text == "Finish")
                {
                    StartActivity(typeof(GameResultActivity));
                }
                else
                {
                    viewModel.NextQuestion();

                    if (viewModel.CurrentQuestionNumber == 5)
                    {
                        _btnNext.Text = "Finish";
                    }

                    // load new question and answers
                    _qn.Text = viewModel.CurrentQuestionNumber + ". question";
                    _q.Text  = viewModel.CurrentQuestion.Text;
                    _adapter.NotifyDataSetInvalidated();
                }
            }
            else
            {
                new AlertDialog.Builder(this)
                .SetTitle(Resource.String.Warning)
                .SetMessage("Please answer first!")
                .SetPositiveButton("OK", (IDialogInterfaceOnClickListener)null)
                .Show();
            }
        }