public ObservableCollection <MeetingRoomModel> GetMeetingRooms(MeetingCenterModel meetingCenter)
        {
            if (_meetingRooms.ContainsKey(meetingCenter))
            {
                return(_meetingRooms[meetingCenter]);
            }
            else
            {
                var collection = new ObservableCollection <MeetingRoomModel>( );
                _meetingRooms[meetingCenter] = collection;

                return(collection);
            }
        }
        public void SetData(Dictionary <IMeetingCenter, ICollection <IMeetingRoom> > dict)
        {
            ClearData( );

            foreach (var center in dict.Keys)
            {
                var centerModel = new MeetingCenterModel(center);
                MeetingCenters.Add(centerModel);

                var roomCollection = new ObservableCollection <MeetingRoomModel>( );

                var rooms = dict[center];
                foreach (var room in rooms)
                {
                    var roomModel = new MeetingRoomModel(room);
                    roomCollection.Add(roomModel);
                }

                _meetingRooms[centerModel] = roomCollection;
            }

            OnPropertyChanged(nameof(MeetingCenters));
            OnPropertyChanged(nameof(_meetingRooms));
        }