public void ChooseQuestionsForTest()
 {
     while (QuestionsRandomlyChoosenForTest.Count < NumberOfQuestionsForThisTest)
     {
         Random r         = new Random();
         int    _question = r.Next(QuestionsInSet.Count);
         if (!QuestionsRandomlyChoosenForTest.Contains(QuestionsInSet[_question]))
         {
             QuestionsRandomlyChoosenForTest.Add(QuestionsInSet[_question]);
         }
     }
 }