Сериализация нескольких разнородных объектов

using (FileStream fs = new FileStream("Save.dat", FileMode.OpenOrCreate))
            {
                formatter.Serialize(fs, AvailebleRoom.Avail);
                formatter.Serialize(fs, AvailebleRoom.Holl);
                formatter.Serialize(fs, AvailebleRoom.Kitchen);
                formatter.Serialize(fs, AvailebleRoom.Cabinet);
                formatter.Serialize(fs, AvailebleRoom.Loft);
                formatter.Serialize(fs, pl.GetCurrRoomForSave());
            }

using (FileStream fs = new FileStream("Save.dat", FileMode.OpenOrCreate))
            {
                AvailebleRoom.Avail.AddRange((List<IRoom>)formatter.Deserialize(fs));
                AvailebleRoom.Holl.AddRange((List<IRoom>)formatter.Deserialize(fs));
                AvailebleRoom.Kitchen.AddRange((List<IRoom>)formatter.Deserialize(fs));
                AvailebleRoom.Cabinet.AddRange((List<IRoom>)formatter.Deserialize(fs));
                AvailebleRoom.Loft.AddRange(((List<IRoom>)formatter.Deserialize(fs));
                Player pl=(Player)formatter.Deserialize(fs);
                return pl;
                
            }

Player pl=(Player)formatter.Deserialize(fs);