优化Linqvar lastOrderIds = from b in DbGetIQueryableCharging_Order where !bDeleted group b by bChargingGunId into g select gOrderByDescendingx = xCh

可以尝试优化这段代码，将其合并为一个查询，避免了两次查询数据库的开销：

var lastOrders = from b in Db.GetIQueryable<Charging_Order>() where !b.Deleted && lastOrderIds.Contains(b.Id) group b by b.ChargingGunId into g select g.OrderByDescending(x => x.ChargingBeginTime).FirstOrDefault();