private void DisplayPage_Initialized(object sender, EventArgs e)
 {
     DisplayPage.Navigate(new CustomersList());
 }
 private void ItemListAppointments_Click(object sender, RoutedEventArgs e)
 {
     DisplayPage.Navigate(new AppointmentsList());
 }
 private void ItemListBrokers_Click(object sender, RoutedEventArgs e)
 {
     DisplayPage.Navigate(new BrokersList());
 }
 private void ItemAddAppointment_Click(object sender, RoutedEventArgs e)
 {
     DisplayPage.Navigate(new AddAppointment());
 }
 private void ItemAddBroker_Click(object sender, RoutedEventArgs e)
 {
     DisplayPage.Navigate(new AddBroker());
 }