C#中的运算符重载和Linq求和

Question

我有一个自定义类型(Money)有一个implict转换为十进制和一个重载运算符+.当我有这些类型的列表并调用linq Sum方法时,结果是十进制,而不是Money.我如何给+运营商总统并从Sum？返回资金？

internal class Test
{
    void Example()
    {
        var list = new[] { new Money(10, "GBP"), new Money(20, "GBP") };
        //this line fails to compile as there is not implicit 
        //conversion from decimal to money
        Money result = list.Sum(x => x);
    }
}


public class Money
{
    private Currency _currency;
    private string _iso3LetterCode;

    public decimal? Amount { get; set; }
    public Currency Currency
    {
        get {  return _currency; }
        set
        {
            _iso3LetterCode = value.Iso3LetterCode; 
            _currency = value; 
        }
    }

    public Money(decimal? amount, string iso3LetterCurrencyCode)
    {
        Amount = amount;
        Currency = Currency.FromIso3LetterCode(iso3LetterCurrencyCode);
    }

    public static Money operator +(Money c1, Money c2)
    {
        if (c1.Currency != c2.Currency)
            throw new ArgumentException(string.Format("Cannot add mixed currencies {0} differs from {1}",
                                                      c1.Currency, c2.Currency));
        var value = c1.Amount + c2.Amount;
        return new Money(value, c1.Currency);
    }

    public static implicit operator decimal?(Money money)
    {
        return money.Amount;
    }

    public static implicit operator decimal(Money money)
    {
        return money.Amount ?? 0;
    }
}

Answer 1

Sum只知道数字类型System.

你可以Aggregate像这样使用:

Money result = list.Aggregate((x,y) => x + y);

因为这是调用Aggregate<Money>,它将使用你的Money.operator+并返回一个Money对象.