private void OnAddFriendExecute()
        {
            var friend = SelectedAvailableFriend;

            Meeting.Model.Friends.Add(friend);
            AddedFriends.Add(friend);
            AvailabileFriends.Remove(friend);
            HasChanges = _meetingRepository.HasChanges();
            ((DelegateCommand)SaveCommand).RaiseCanExecuteChanged();
        }
        private void SetupPicklist()
        {
            var meetingFriendIds = Meeting.Model.Friends.Select(f => f.Id).ToList();
            var addedFriends     = _allFriends.Where(f => meetingFriendIds.Contains(f.Id)).OrderBy(f => f.FirstName);
            var availableFriends = _allFriends.Except(addedFriends).OrderBy(f => f.FirstName);

            AddedFriends.Clear();
            AvailabileFriends.Clear();

            foreach (var addedFriend in addedFriends)
            {
                AddedFriends.Add(addedFriend);
            }

            foreach (var availableFriend in availableFriends)
            {
                AvailabileFriends.Add(availableFriend);
            }
        }