var APPQuery = aa.query(); var ValidQuery = bb.query();var query = from o in APPQueryjoin v in ValidQueryon o.Id equals v.Id into resultfrom r in result.DefaultIfEmpty()select new GetFlightDto{Calsign = r.Calsign........};
ps: GetFlightDto 是定义好的类库,APPQuery ,ValidQuery 为数据库取出的数据对象