linq - linqで複数の外部左結合を記述する方法は?

Question

複数のテーブルを外部結合しようとしています。ここに、私がやろうとしているコードを貼り付けました。

from o in entities.O
                             join p in entities.P on o.PID equals p.ID
                             join dC in entities.C on o.DCID equals dC.ID
                             join hC in entities.C on o.HCID equals hC.ID
                             join e in entities.E on pat.AN equals e.UID
                             join oT in entities.OT on o.OT equals oT.ID
                             join plt in entities.PLT on p.LT equals plt.ID
                             join puO in entities.PUO on o.PUTId equals puO.ID into pots
                             from x in pots.DefaultIfEmpty()
                             join op in entities.OP on o.OPID equals op.ID
                             join prt in entities.PatientRelationshipTypes on pat.PRTId equals prt.ID
                             join secPRT in entities.PRT on pat.SRTId equals secPRT.ID
                             join patDiagCode in entities.PDiagnosisCodes on pat.ID equals patDiagCode.PID
                             //from y in pdc.DefaultIfEmpty()
                             join diagCode in entities.DCodes on patDiagCode.CodeID equals diagCode.ID into dc
                             from z in dc.DefaultIfEmpty()
                             where o.ID == orderId
                             //from x in pots.DefaultIfEmpty()
                             //from y in pdc.DefaultIfEmpty()
...
...

Linqで複数の外部結合の正しい構文を書くにはどうすればよいですか?

前もって感謝します