NHibernate使用入门(六)

预加载、延迟加载

其他相关类和配置文件参考入门（五）

EagerLoading.cs预加载类:

 public class EagerLoading 
    {
        ISessionFactory sessionFactory = new Configuration().Configure().BuildSessionFactory();
protected object CustomerId=1;
public void EagerLoadingCollection()
        {
using (var session = sessionFactory.OpenSession())
            {
                Customer customer = session.Get<Customer>(CustomerId);

if (customer.Orders.Count>0)
                {
                    customer.Orders.ForEach(o=> Console.WriteLine(o.Id));
                }

            }
        }


public void EagerLoadingCollectionAfterSession()
        {
            Customer customer;
using (var session = sessionFactory.OpenSession())
            {
                customer = session.Get<Customer>(CustomerId);
            }

if (customer.Orders.Count > 0)
            {
                customer.Orders.ForEach(o => Console.WriteLine(o.Id));
            }

        }
    }

LazyLoading.cs延迟加载类：

 public class LazyLoading 
    {
        ISessionFactory sessionFactory = new Configuration().Configure().BuildSessionFactory();
protected object CustomerId = 1;
public void  LazyLoadingCollection()
        {
using (var session = sessionFactory.OpenSession())
            {
                Customer customer = session.Get<Customer>(CustomerId);

if (customer.Orders.Count > 0)
                {
                    customer.Orders.ForEach(o => Console.WriteLine(o.Id));
                }
            }
        }

//延迟加载，可能会引起session已经关闭的异常，例如：

//当实现延迟加载，当需要Orders时，会通过session去查询，session。但此时，由于session已经关闭，
//所以会抛出异常：no session or session was closed
public void  LazyLoadingCollectionAfterInitialization()
        {
            Customer customer;
using (var session = sessionFactory.OpenSession())
            {
                customer = session.Get<Customer>(CustomerId);
//强制立即加载
                NHibernateUtil.Initialize(customer.Orders);

            }

if (customer.Orders.Count > 0)
            {
                customer.Orders.ForEach(o => Console.WriteLine(o.Id));
            }
        }


public void LazyLoadingCollectionAfterSession()
        {
            Customer customer;
using (var session = sessionFactory.OpenSession())
            {
                customer = session.Get<Customer>(CustomerId);
            }
            NHibernateUtil.IsInitialized(customer.Orders);
if (customer.Orders.Count > 0)
            {
                customer.Orders.ForEach(o => Console.WriteLine(o.Id));
            }
        }
    }

程序主入口

 class Program
 {
 static void Main(string[] args)
 {
 //---------------------------------------------------
 //EagerLoading el=new EagerLoading();
 //el.EagerLoadingCollection();
 //el.EagerLoadingCollectionAfterSession();
 //---------------------------------------------------
LazyLoading lz = new LazyLoading();
 lz.LazyLoadingCollection();
 lz.LazyLoadingCollectionAfterInitialization();
 lz.LazyLoadingCollectionAfterSession();
 //---------------------------------------------------
 //---------------------------------------------------
 //---------------------------------------------------
 //---------------------------------------------------
 //---------------------------------------------------
 //---------------------------------------------------
Console.ReadKey();
 }
 }