/// <summary>
        /// Updates the LessonsTableData with the lessons of the SelectedSearchChoice
        /// </summary>
        private void UseSelectedSearchChoice()
        {
            if (SelectedSearchChoice != NOT_ASSIGNED)
            {
                // Clean lessons table before adding items to it
                LessonsTableData.Clear();

                // Check which category the search choice is from, and fill the LessonsTableData with the relevent lessons
                if (SearchingByClass)
                {
                    // Find the class that was chosen, and get its lessons
                    _schoolData.Classes.Find(SelectedSearchChoice).Lessons.ToList().
                    ForEach(lesson => LessonsTableData.Add(ModelLessonToLessonData(lesson)));
                }
                else if (SearchingByCourse)
                {
                    // Find the course that was chosen, and get its lessons
                    _schoolData.Courses.Find(SelectedSearchChoice).Lessons.ToList().
                    ForEach(lesson => LessonsTableData.Add(ModelLessonToLessonData(lesson)));
                }
                else if (SearchingByTeacher)
                {
                    // Find the teacher that was chosen, and get his/hers lessons
                    _schoolData.Teachers.Find(SelectedSearchChoice).Lessons.ToList().
                    ForEach(lesson => LessonsTableData.Add(ModelLessonToLessonData(lesson)));
                }
                else
                {
                    // Unknown search category - don't show any lesson
                }
            }
        }
 /// <summary>
 /// Assistant method that clears all the ViewModel properties
 /// </summary>
 private void ResetData()
 {
     AvailableSearchChoices.Clear();
     LessonsTableData.Clear();
     AvailableClasses.Clear();
     AvailableCourses.Clear();
     AvailableTeachers.Clear();
     AvailableRooms.Clear();
     SelectedLesson       = null;
     SelectedSearchChoice = NOT_ASSIGNED;
     SelectedTeacher      = NOT_ASSIGNED;
     SelectedClass        = NOT_ASSIGNED;
     LessonFirstDay       = NOT_ASSIGNED;
     LessonSecondDay      = NOT_ASSIGNED;
     LessonThirdDay       = NOT_ASSIGNED;
     LessonFourthDay      = NOT_ASSIGNED;
     LessonFirstHour      = NOT_ASSIGNED;
     LessonSecondHour     = NOT_ASSIGNED;
     LessonThirdHour      = NOT_ASSIGNED;
     LessonFourthHour     = NOT_ASSIGNED;
 }