目的地类：

public class Policy
     {
         private Billing _billing;

         protected Billing Billing
             {
                get { return _billing; }
                set { _billing = value; }
             }

         public void SetBilling(Billing billing)
            {
                if (billing != null)
                {
                    Billing = billing;
                }
                else
                {
                    throw new NullReferenceException("Billing can't be null");
                }
            }
    }

以下是我的Automapper代码(伪代码)：

Mapper.CreateMap<PolicyDetail,Policy>()
          .ForMember(d => d.SetBilling(???),s => s.MapFrom(x => x.Billing));

我需要通过一个账单类到SetBilling(结算结算)方法.我该怎么做？或者,我可以设置受保护的Billing属性吗？