Dtos, Value Objects, Casting and You

gistfile1.cs

[DataContract]
public class MoneyDto {
	[DataMember(Order = 1)] public readonly decimal Amount;
	[DataMember(Order = 2)] public readonly string CurrencyCode;
	public CurrrencyDto(decimal amount, string currencyCode) {
		Amount = amount;
		CurrencyCode = currencyCode;
	}
}
[DataContract]
public class ConvertMoney : Command {
	[DataMember(Order = 1)] public MoneyDto MyMoney;
	[DataMember(Order = 2)] public string ToMoney;
	public ConvertMoney(MoneyDto myMoney, string toMoney) {
		MyMoney = myMoney;
		ToMoney = toMoney;
	}
}

public class Money {
	static readonly IEnumerable<string> CurrencyCodes = ...;
	private readonly decimal _amount;
	private readonly string _currencyCode;
	public Money(decimal amount, string currencyCode) {
		Guard.AgainstNull(currencyCode, "currencyCode");
		Guard.Against<ArgumentException>(false == CurrencyCodes.Contains(currencyCode), "currencyCode");
		
		_amount = amount;
		_currencyCode = currencyCode;
	}
	
	public Money Convert(string currencyCode, Func<Money, string, decimal> convert) {
		var result = convert(this, currencyCode);
		
		return new Money(result, currencyCode);
	}
	
	public static implicit operator Money(MoneyDto dto) {
		return new Money(dto.Amount, dto.CurrencyCode);
	}
	public static implicit operator MoneyDto(Money money) {
		return new MoneyDto(money._amount, money._currencyCode);
	}

}

void Handle(ConvertMoney command) {
	Money money = command.MyMoney;
	
	var converted = money.Convert(command.ToMoney, this.ConverterService);
	
	bus.Publish(...);
}

// bus.Send(new ConvertMoney(new Money(10, "USD"), "LOL")); // throws because invariants