private void AddToPersonIndex(Participant participant)
{
DoubleList <Book> bookDoubleList = new DoubleList <Book>();
participant.WishList.ForEach(b => bookDoubleList.AddToWish(b));
participant.GiveList.ForEach(b => bookDoubleList.AddToGive(b));
personIndex.Add(participant.Person, bookDoubleList);
}
