public override string ToString()
 {
     return($"Reservation:\n\tid: {Id.ToString()}\n\tperformance id: {PerformanceId.ToString()}\n\tdate of reservation: {Date.Day.ToString()}/{Date.Month.ToString()}/{Date.Year.ToString()}" +
            $"\n\tnumber of tickets:{TicketQuantity.ToString()}\n\tstate of reservation: {State.ToString()}\n\n");
 }
 public string Write()
 {
     return($"{Id.ToString()};{PerformanceId.ToString()};{Date.Day.ToString()}/{Date.Month.ToString()}/{Date.Year.ToString()};{TicketQuantity.ToString()};{State.ToString()};{Environment.NewLine}");
 }