var query=from ep in JHExamPaper
          join p in Paper on ep.PaperId equals p.Id
          join s in Subject on p.SubjectId equals s.Id
          join eps in ExamPaperStudent on ep.PaperId equals eps.PaperId into leftJoinGroup
          from eps in leftJoinGrou.DefaultIfEmpty()
          join r in Report on eps.Id equlas r.EPSId into Left
          from r in Left.DefalutIfEmpty()
          where eps.ExamId=="B39A5BEE-8021-4A0D-8CC2-4BDEFC580579" && eps.UserId=="110813D3-AF1D-41A2-9F39-B44604CA2BC6"
          select new 
          {
            p.Id,r.Id,s.Id,s.Name,p.Title,p.TotalScore 
          };