private void LearnDictionary()
        {
            int selectedDictionary = GetSelectedDictionaryId();
            if (selectedDictionary < 1)
                return;

            try
            {
                LearningWindow learningWindow = new LearningWindow(new Dictionary(selectedDictionary, "", 0, 0, ""), WordsInLesson, AnswersForLearnedWords);
                learningWindow.ShowDialog();
            }
            catch
            {
                //MessageBox.Show("Can't start learning", "Learning Window", MessageBoxButton.OK, MessageBoxImage.Error);
            }
        }
        private void LearnVocabulary()
        {
            int selectedVocabulary = GetSelectedVocabularyId();
            if (selectedVocabulary < 1)
                return;

            try
            {
                LearningWindow learningWindow = new LearningWindow(new Vocabulary(selectedVocabulary, "", 0, ""), WordsInLesson, AnswersForLearnedWords);
                learningWindow.ShowDialog();
                UpdateVocabulariesList();
            }
            catch
            {
                //MessageBox.Show("Error", "Learning Window", MessageBoxButton.OK, MessageBoxImage.Error);
            }
        }