private void OnRemovePerson()
 {
     foreach (string selectedPersonToRemove in PeopleToRemove)
     {
         if (PeopleForAdding.Contains(selectedPersonToRemove))
         {
             PeopleForAdding.Remove(selectedPersonToRemove);
         }
     }
 }
 private void OnAddPerson()
 {
     if (SelectedPersonToAdd == null)
     {
         messageForUser("Please select a person and try again", "No person selected");
     }
     else if (!PeopleForAdding.Contains(SelectedPersonToAdd))
     {
         PeopleForAdding.Add(SelectedPersonToAdd);
     }
     else
     {
         messageForUser("Person already added", "Warning");
     }
     SelectedPersonToAdd = null;
 }