1      var query =(from t1 in db.table1 2                  join t2 in db.table2 3                  on new {ID=t1.ID1,UserID=t1.ID2} 4                  equal new {ID=t2.LID1,UserID=t2.LID2} 5                  into temp 6                  from t in temp.DefaultIfEmpty() 7                  where t1.ID1=99 8                  orderby t1.V1 descending 9                  select new10                  {11                         t1.ID1,12                         t1.ID2,13                         t1.V1,14                         t.V2 ??  015                  }).ToList();