/// <summary>
 /// handler for comboBoxDoctors SelectionChanged Event,
 /// gets selected Doctor and find his schedule using ScheduleService
 /// build a string with his schedule and show the schedule to the user, in order to select a proper time for his appointment
 /// </summary>
 private void comboBoxDoctors_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     if (comboBoxDoctors.SelectedItem != null)
     {
         List <Schedule> schedule = _scheduleService.FindAllByProperty(Utils.ScheduleTableProperties.IdDoctor, ((ComboBoxItem)comboBoxDoctors.SelectedItem).Tag.ToString());
         String          sch      = "";
         foreach (Schedule s in schedule)
         {
             sch += (DayOfWeek)(s.Day) + "\t" + s.StartHour + "-" + s.EndHour + "\n";
         }
         labelScheduleTitle.Visibility   = Visibility.Visible;
         labelScheduleContent.Visibility = Visibility.Visible;
         labelScheduleContent.Content    = sch;
     }
 }