left join linq

一直沒弄明白linq 的左鏈接查詢，終於找到解決方案了：

var result = (from a in table1

           join b in table2 on a.a_guid equals b.b_guid into t1


           from b in t1.DefaultIfEmpty()


           join c in table3 on a.a_guid equals c.c_guid into t2


           from c in t2.DefaultIfEmpty()


           join e in table4 on a.a_userid equals e.e_userid into t3


           from e in t3.DefaultIfEmpty()


           orderby a.CreateWhen


select new {....});