如何使绑定更新,特别是对于派生值?

漂亮的样板:

protected void RaisePropertyChanged(string propertyName)
{
    if (PropertyChanged != null)
    {
        PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
    }
}

    private double m_TotalWidgets = 0;
    public double TotalWidgets
    {
        get { return m_TotalWidgets; }
        set 
        { 
            m_TotalWidgets = value;
            RaisePropertyChanged("TotalWidgets");
        }
    }

假设我有一个计算值:

    public double ScaledWidgets
    {
        get 
        { 
            return TotalWidgets * CONSTANT_FACTOR;
        }
    }

当TotalWidgets更新时,我必须启动ScaledWidget的PropertyChanged,例如:

        set 
        { 
            m_TotalWidgets = value;
            RaisePropertyChanged("TotalWidgets");
            RaisePropertyChanged("ScaledWidgets");
        }

有没有更好的办法?是否有可能使整个对象“失效”,特别是在有很多派生值的情况下?我觉得炒100个财产变更事件有点不靠谱。