我有一个自定义类型(Money),它具有对十进制的隐含转换和一个重载的运算符.当我有这些类型的列表并调用
linq Sum方法结果是十进制,而不是金钱.如何给予经营者前提,并从金额返还资金？
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;
}
}
解决方法
总和只知道系统中的数字类型.
你可以这样使用Aggregate：
Money result = list.Aggregate((x,y) => x + y);
因为这是调用Aggregate< Money>,它将使用您的Money.operator并返回一个Money对象.