Question

我在DB中有两个表，我想从中选择。在其中一个'事件'中我有事件（Id，开始，结束，类型），另一个我有'Events_before_after'，我收集与'Events'中的一些事件相关联的事件 - （Id，EventId，开始，结束，类型）我还有一个事件ID列表，我需要通过它来选择查询中的事件。

这就是我所拥有的：

List<int> orderIds = ...

from order in orderIds
join event in events order on order equals event.id
select new DataEvent ()
{
    eventId = event.Id,
    start = event.start,
    end = event.end,
    type = event.type
}).Concat
from eventOther in Events_before_after
select new DataEvent ()
{
    eventId = eventOther.Id,
    start = eventOther.start,
    end = eventOther.end,
    type = eventOther.type
}

是否可以订购第二个选择？我的意思是 - 有没有办法按eventId订购，链接到'活动'？

我需要的是：

event1
event2
eventBefore3
event3
eventAfter3

我所拥有的是：

event1
event2
event3
eventBefore3
eventAfter3

Answer 1

你可以这样做：

 //your query
 ...
from eventOther in Events_before_after
select new DataEvent ()
{
    eventId = eventOther.Id,
    start = eventOther.start,
    end = eventOther.end,
    type = eventOther.type
}
into NewEvent
order by NewEvent.eventId
select NewEvent;

Answer 2

如果我得到你的要点，你想要将给定键上的相关事件组合在一起，对它们进行排序，然后根据给定的键排序进行投影和展平....如果你想这样做，请尝试以下方法：

var orderedEvents = orderIds.Join(
                     //Construct Groups 
                     events.GroupBy( e => e.Id)
                           .GroupJoin( Events_before_after,
                                       g => g.Key,
                                       e => e.EventId,
                                       (gEvent, gEventBA) => new { Key = gEvent.Key,
                                       EventGroup = 
                                       gEvent.Select( e => new DataEvent ()
                                                     {
                                                      eventId = e.Id,
                                                      start = e.start,
                                                      end = e.end,
                                                      type = e.type
                                                     })
                                              .Concat( gEventBA.Select( e => new DataEvent ()
                                                                {
                                                                 eventId = e.Id,
                                                                 start = e.start,
                                                                 end = e.end,
                                                                 type = e.type
                                                                }))
                                              .OrderBy(e => e.eventId)),
                      //Project along keys
                      o => o,
                      anon => anon.Key,
                      (o,anon) => anon.EventGroup)
                      //Flatten groups
                           .SelectMany( g => g);

Linq按列表顺序从两个表中选择

2 个答案: