private void ManyTestCheckAnswer()
        {
            bool   checked1 = (bool)manyTestMode_Page2_answer1.IsChecked;
            bool   checked2 = (bool)manyTestMode_Page2_answer2.IsChecked;
            bool   checked3 = (bool)manyTestMode_Page2_answer3.IsChecked;
            bool   checked4 = (bool)manyTestMode_Page2_answer4.IsChecked;
            String answers  = "";

            if (checked1)
            {
                answers += "0";
            }
            if (checked2)
            {
                answers += "1";
            }
            if (checked3)
            {
                answers += "2";
            }
            if (checked4)
            {
                answers += "3";
            }
            if (answers != "")
            {
                manyTest.CheckAnswer(questionIndex - 1, answers);
            }
        }