/*
  * Creates new guest or decorates current customer according to window
  * TextBoxes contents.
  */
 private void createGuest()
 {
     if (!this.isCustomer) // create and add new guest
     {
         mFacade.AddGuest(txtName.Text,
                          txtPassportNb.Text,
                          Int32.Parse(txtAge.Text));
     }
     else // decorate current customer as guest and add to list
     {
         mFacade.AddCustomerToGuests(txtPassportNb.Text,
                                     Int32.Parse(txtAge.Text));
     }
 }