Question

我有一个扩展方法，检查对象的类型，然后填充其成员属性

public static void LoadMeeting<T>(this T entity, IMeetingRepository meetingRepository) 
where T: MyEntity
            {
                var agenda = entity as Agenda;

                if (agenda != null)
                {
                    agenda.Meeting = meetingRepository.GetMeetingById(agenda.MeetingId);
                }

                var participant = entity as Participant;

                if (participant != null)
                {
                    participant.Meeting = meetingRepository.GetMeetingById(participant.MeetingId);
                }

            }

我可以进一步将其重构为类似的内容以使其更通用吗？

 public static void LoadMeeting<T>(this T entity, IMeetingRepository meetingRepository) where T : MyEntity
        {
            var obj = entity as Agenda || entity as Participant;

            if (obj != null)
            {
                obj.Meeting = meetingRepository.GetMeetingById(obj.MeetingId);
            }
        }
    }

PS：我不想把对象的属性Meeting放在Base类中（MyEntity）

Answer 1

我个人只会使用重载：

public static void LoadMeeting(this Agenda agenda, IMeetingRepository meetingRepository) 
{
    if (agenda != null)
    {
         agenda.Meeting = meetingRepository.GetMeetingById(agenda.MeetingId);
    }
}
public static void LoadMeeting(this Participant participant, IMeetingRepository meetingRepository) 
{
    if (participant != null)
    {
        participant.Meeting = meetingRepository.GetMeetingById(participant.MeetingId);
    }
}

除非您有一些提供Meeting属性的共享契约（基类或接口实现），否则您无法使用单个泛型方法执行此操作。

替代方案是创建一个共享接口，即：IMeeting，然后约束到：

public interface IMeeting
{
   public Meeting Meeting { get; set; }
   public int MeetingId { get; }
}

然后你可以写：

public static void LoadMeeting<T>(this T entity, IMeetingRepository meetingRepository)

其中T：IMeeting { if（entity！= null） { entity.Meeting = meetingRepository.GetMeetingById（entity.MeetingId）; } }

当您使用EF时，您可以在部分类中实现此接口：

public partial class Agenda : MyEntity, IMeeting
{
}

Answer 2

您可能希望尽早返回该方法，因为您必须处理类及其基类。

public static void LoadMeeting<T>(this T entity, IMeetingRepository meetingRepository) where T: MyEntity
        {
            var agenda = entity as Agenda;

            if (agenda != null)
            {
                agenda.Meeting = meetingRepository.GetMeetingById(agenda.MeetingId);
                return;
            }

            var participant = entity as Participant;

            if (participant != null)
            {
                participant.Meeting = meetingRepository.GetMeetingById(participant.MeetingId);
                return;
            }
        }

您可能还会考虑表格方法：

    public static void LoadMeeting<T>(this T entity, IMeetingRepository meetingRepository) where T: MyEntity {
        var name = entity.GetType().Name;
        if (Table.ContainsKey(name)) {
            Table[name](entity, meetingRepository);
            }
        }

表格是：

static Dictionary<String, Action<MyEntity, IMeetingRepository>> Table = new Dictionary<String, Action<MyEntity, IMeetingRepository>>();

它被初始化为：

        Table.Add("Agenda", (agenda, meetingRepository) => { 
            ((Agenda)agenda).Meeting = meetingRepository.GetMeetingById(((Agenda)agenda).MeetingId); }); 
        Table.Add("Participant", (participant, meetingRepository) => { 
            ((Participant)participant).Meeting = meetingRepository.GetMeetingById(((Participant)participant).MeetingId); });

显然，您的表必须是静态的，并且可用于您的扩展方法（例如在包含类中）。

重构：通用扩展方法

2 个答案: