if (voucher.ServiceType == ServiceType.VaccineCompany)
            {
                if (voucher.Asignee == null)
                {
                    throw new ArgumentNullException("Asignee is required for company vaccine voucher");
                }
                if (!voucher.BookingTime.HasValue)
                {
                    throw new ArgumentNullException("Booking time is required for company vaccine voucher");
                }
                if (!voucher.FixedPrice.HasValue)
                {
                    throw new ArgumentNullException("Fixed price is required for company vaccine voucher");
                }
                if (voucher.Discount.HasValue)
                {
                    throw new ArgumentNullException("Discount is not a valid argument for company vaccine type voucher");
                }
            }

            if (voucher.ServiceType == ServiceType.Vaccine)
            {
                if (voucher.Asignee != null)
                {
                    throw new ArgumentException("Invalid argument asignee");
                }
                if (voucher.BookingTime.HasValue)
                {
                    throw new ArgumentNullException("Invalid argument booking time");
                }
                if (voucher.FixedPrice.HasValue && voucher.Discount.HasValue)
                {
                    throw new ArgumentException("Fixed price and discount cannot be set simultaneously");
                }
            }

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Runtime.Serialization;

namespace Remoting.VoucherService
{
    [DataContract]

    public sealed class Voucher
    {
        [Required(ErrorMessage = "Code is required")]
        [DataMember(Name = "code")]
        public string Code { get; set; }

        [Required(ErrorMessage = "Description is required")]
        [DataMember(Name = "description")]
        public string Description { get; set; }

        [Required(ErrorMessage = "ServiceType is required")]
        [DataMember(Name = "serviceType")]
        public ServiceType ServiceType { get; set; }

        [DataMember(Name = "discount")]
        public double? Discount { get; set; }

        [DataMember(Name = "fixedPrice")]
        public double? FixedPrice { get; set; }

        [DataMember(Name = "isValid")]
        public bool Valid {
            get { return TimesUsed < MaxUsage; }
            set { }
        }

        [DataMember(Name = "maxUsage")]
        public uint MaxUsage { get; set; } = 1;

        [DataMember(Name = "asignee")]
        public string Asignee;

        [DataMember(Name = "bookingTime")]
        public DateTime? BookingTime;

        [DataMember(Name = "timesUsed")]
        public uint TimesUsed { get; set; } = 0;

        public void IncreaseUsage()
        {
            TimesUsed += 1;
        }

        private ExtensionDataObject data;

        public ExtensionDataObject ExtensionData
        {
            get => data;
            set => data = value;
        }
    }
}