為什么下面這段代碼中的Persist方法，每次都立即在SQL Server中執行Insert語句？我用的是Nhibernate3.2         [TestMethod]         public void oneToManyTest()         {             Customer c1 = _session.Get<Customer>(1);;             for (int i = 0; i < 13; i++)             {                 Order o = new Order() { Customer = c1, OrderDate = DateTime.Now};                 c1.Orders.Add(o);                 _session.Persist(o);             }                        _session.Flush();         }