public override string ToString() { return($"ID [{Id}] Customer [{Customer}] No. Rented Books [{RentedBooks?.Count() ?? 0}]"); }
public override string ToString() { return($"ID [{Id} Name [{Name}] IdentityNumber [{IdentityNumer}] Address [{Adress}] PhoneNumber [{PhoneNumber}] No. Books [{RentedBooks?.Count() ?? 0}]"); }