问题 DDD实体利用服务

我有一个应用程序，我正在尝试用至少一个名义上的DDD类型域模型构建，并且正在与某个部分进行斗争。

我的实体有一些业务逻辑，它使用我目前在某些域服务中的一些财务计算和速率计算，以及我在一个值对象中放置的一些常量值。

我正在努力解决如何让实体使用域服务中的逻辑，或者这些服务中的逻辑是否属于那里。这是我到目前为止：

public class Ticket
{
    public Ticket(int id, ConstantRates constantRates, FinancialCalculationService f, RateCalculationService r)
    {
        Id = id;
        ConstantRates = constantRates;
        FinancialCalculator = f;
        RateCalculator = r;
    }

    private FinancialCalculationService FinancialCalculator { get; set; }

    private RateCalculationService RateCalculator { get; set; }

    private ConstantRates ConstantRates { get; set; }

    public int Id { get; private set; }

    public double ProjectedCosts { get; set; }

    public double ProjectedBenefits { get; set; }

    public double CalculateFinancialGain()
    {
        var discountRate = RateCalculator.CalculateDiscountRate(ConstantRates.Rate1, ConstantRates.Rate2,
                                                                ConstantRates.Rate3);

        return FinancialCalculator.CalculateNetPresentValue(discountRate,
                                                            new[] {ProjectedCosts*-1, ProjectedBenefits});
    }
}


public class ConstantRates
{
    public double Rate1 { get; set; }
    public double Rate2 { get; set; }
    public double Rate3 { get; set; }
}

public class RateCalculationService
{
    public double CalculateDiscountRate(double rate1, double rate2, double rate3 )
    {
        //do some jibba jabba
        return 8.0;
    }
}

public class FinancialCalculationService
{
    public double CalculateNetPresentValue(double rate, params double[] values)
    {
        return Microsoft.VisualBasic.Financial.NPV(rate, ref values);
    }

}

我觉得某些计算逻辑确实属于那些域服务，但不是真的喜欢我必须从我的存储库手动注入这些依赖项。是否有另一种方式可以建模？我不喜欢那个吗？

读过蓝皮书但之前没有真正构建过这种风格的东西，我正在寻找指导。

编辑

谢谢大家的反馈！基于我所听到的，听起来我的模型看起来应该更像下面的内容。这看起来更好？

public class Ticket
{
    public Ticket(int id)
    {
        Id = id;
    }

    private ConstantRates ConstantRates { get; set; }

    public int Id { get; private set; }

    public double ProjectedCosts { get; set; }

    public double ProjectedBenefits { get; set; }

    public double FinancialGain { get; set; }
}



public class ConstantRates
{
    public double Rate1 { get; set; }
    public double Rate2 { get; set; }
    public double Rate3 { get; set; }
}

public class FinancialGainCalculationService
{
    public FinancialGainCalculationService(RateCalculationService rateCalculator, 
        FinancialCalculationService financialCalculator,
        ConstantRateFactory rateFactory)
    {
        RateCalculator = rateCalculator;
        FinancialCalculator = financialCalculator;
        RateFactory = rateFactory;
    }

    private RateCalculationService RateCalculator { get; set; }
    private FinancialCalculationService FinancialCalculator { get; set; }
    private ConstantRateFactory RateFactory { get; set; }

    public void CalculateFinancialGainFor(Ticket ticket)
    {
        var constantRates = RateFactory.Create();
        var discountRate = RateCalculator.CalculateDiscountRate(constantRates.Rate1, constantRates.Rate2,
                                                                constantRates.Rate3);

        ticket.FinancialGain = FinancialCalculator.CalculateNetPresentValue(discountRate,
                                                            new[] {ticket.ProjectedCosts*-1, ticket.ProjectedBenefits});
    }
}

public class ConstantRateFactory
{
    public ConstantRates Create()
    {
        return new ConstantRates();
    }
}

public class RateCalculationService
{
    public double CalculateDiscountRate(double rate1, double rate2, double rate3 )
    {
        //do some jibba jabba
        return 8.0;
    }
}

public class FinancialCalculationService
{
    public double CalculateNetPresentValue(double rate, params double[] values)
    {
        return Microsoft.VisualBasic.Financial.NPV(rate, ref values);
    }

}

域模型在这一点上最终变得相当贫乏，但是当我添加功能时，它可能会有更多功能。

编辑2

好的，我得到了更多的反馈，也许我的“计算”服务更像是战略对象，我的实体可以依赖它。这是对实体的更多逻辑的另一种看法，并利用这些策略对象。对此的想法？直接在实体中实例化这些助手的任何问题？我认为我不想在我的测试中嘲笑那些，但OTOH我也无法在不测试这些策略对象的情况下测试CalculateFinancialGain方法。

public class Ticket
{
    public Ticket(int id, ConstantRates constantRates)
    {
        Id = id;
        ConstantRates = constantRates;
    }

    private ConstantRates ConstantRates { get; set; }

    public int Id { get; private set; }

    public double ProjectedCosts { get; set; }

    public double ProjectedBenefits { get; set; }

    public double CalculateFinancialGain()
    {
        var rateCalculator = new RateCalculator();
        var financeCalculator = new FinanceCalculator();
        var discountRate = rateCalculator.CalculateDiscountRate(ConstantRates.Rate1, ConstantRates.Rate2,
                                                                ConstantRates.Rate3);

        return financeCalculator.CalculateNetPresentValue(discountRate,
                                                            ProjectedCosts*-1, 
                                                            ProjectedBenefits); 
    }
}

public class ConstantRates
{
    public double Rate1 { get; set; }
    public double Rate2 { get; set; }
    public double Rate3 { get; set; }
}

public class RateCalculator
{
    public double CalculateDiscountRate(double rate1, double rate2, double rate3 )
    {
        //do some jibba jabba
        return 8.0;
    }
}

public class FinanceCalculator
{
    public double CalculateNetPresentValue(double rate, params double[] values)
    {
        return Microsoft.VisualBasic.Financial.NPV(rate, ref values);
    }

}