实体框架 OrderBy 日期列表

Question

在实体框架中，我如何使用MeetingDateList select 最新会议？

我尝试使用.OrderByDescending(y => y.MeetingDateList.Select(x => x.StartDate))但出现错误。

错误 DbSortClause 表达式必须具有顺序可比的类型。\r\n参数名称: key"}

select new Model.Meeting
       {
           MeetingId = i.MeetingId,
           MeetingDateList = (from m in db.MeetingDates
                              where i.MeetingId == m.MeetingId
                              orderby m.MeetingDateId
                              select new Model.MeetingDate
                                     {
                                         MeetingDateId = m.MeetingDateId,
                                         StartDate = m.StartDate.ToString(),
                                         StartTime = m.StartTime.ToString(),
                                     }).ToList(),
       })
       .OrderByDescending(y => y.MeetingDateList.Select(x => x.StartDate))
       .FirstOrDefault();

Answer 1

我猜您想按该列表中最新的 MeetingDate-StartDate 进行订购，因此请使用Max ：

.OrderByDescending(y => y.MeetingDateList.Select(x => x.StartDate).Max())