LINQ 左右连接

LINQ 左右连接：DefaultIfEmpty()

incomeList = (from p in db.Incomes
                              join m in db.Items
                              on p.ItemID equals m.ID into tempResult
                              from m in tempResult.DefaultIfEmpty()
                              select new IncomeItem
                              {
                                  ID = p.ID,
                                  ItemID = p.ItemID,
                                  IncomeMoney = p.IncomeMoney,
                                  CreateTime = p.CreateTime,
                                  UpdateTime = p.UpdateTime,
                                  ItemCode = m.ItemCode,
                                  ItemName = m.ItemName
                              }).ToList();