NHibernate系列文章三：简单的增删改查询

摘要

上一篇文章只完成了简单的NHibernate安装、配置和连接数据库。这篇文章介绍怎样实现最简单的数据库读写操作。

1. 重构ISessionFactory生成过程

将生成ISessionFactory的代码从main函数中移除，变成使用属性控制。

         private static ISessionFactory _sessionFactory;

         public static ISessionFactory SessionFactory
         {
             get
             {
                 if (_sessionFactory == null)
                 {
                     var cfg = new Configuration();

                     cfg.DataBaseIntegration(x =>
                     {
                         x.ConnectionString = "Data Source=localhost;Initial Catalog=NHibernateDemoDB;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False";
                         x.Driver<SqlClientDriver>();
                         x.Dialect<MsSql2008Dialect>();
                     });
                     cfg.AddAssembly(Assembly.GetExecutingAssembly());
                     _sessionFactory = cfg.BuildSessionFactory();
                 }
                 return _sessionFactory;
             }
         }  

SessionFactory的创建很占用系统资源，一般在整个应用程序中只创建一次。因此，这里通过判断if (_sessionFactory == null)实现一个最简单的单例模式。

2. GetAll和GetById函数代码

         private static IList<Customer> GetAll()
         {
             using (var session = SessionFactory.OpenSession())
             {
                 IList<Customer> list = session.CreateCriteria<Customer>().List<Customer>();
                 return list;
             }
         }

         private static Customer GetById(int id)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 Customer customer = session.Get<Customer>(id);
                 return customer;
             }
         }

使用using子句，在using代码块完成后，将自动调用ISession的Dispose方法关闭Session

3. 增删改函数代码

         private static int Insert(Customer customer)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 var identifier = session.Save(customer);
                 session.Flush();
                 return Convert.ToInt32(identifier);
             }
         }

         private static void Update(Customer customer)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 session.SaveOrUpdate(customer);
                 session.Flush();
             }
         }

         private static void Delete(int id)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 var customer = session.Load<Customer>(id);
                 session.Delete(customer);
                 session.Flush();
             }
         }

• session.Save: 插入新记录，返回新纪录主键值
• session.SaveOrUpdate: 如果被调用的Customer对象在数据库里不存在（新记录），则插入新记录，否则修改该记录
• session.Delete: 传入Customer对象进行删除
• 增删改操作完成之后需要调用session.Flush()方法，将对象持久化写入数据库。如果不调用此方法，方法结束后修改记录不能写入到数据库

4. 添加方法CreateCustomer

         private static Customer CreateCustomer()
         {
             var customer = new Customer
             {
                 FirstName = "Daniel",
                 LastName = "Tang",
                 Points = ,
                 HasGoldStatus = true,
                 MemberSince = new DateTime(, , ),
                 CreditRating = CustomerCreditRating.Good,
                 AverageRating = 42.42424242,
                 Street = "123 Somewhere Avenue",
                 City = "Nowhere",
                 Province = "Alberta",
                 Country = "Canada"
             };

             return customer;
         }

5. 修改main函数

         static void Main(string[] args)
         {
             Customer newCustomer = CreateCustomer();
             int customerId = Insert(newCustomer);
             Console.WriteLine("new customer id: {0}", customerId);

             IList<Customer> list = GetAll();
             Console.WriteLine("customer list count: {0}", list.Count);
             foreach(var item in list)
             {
                 Console.WriteLine("{0} {1}", item.FirstName, item.LastName);
             }

             var customer = GetById(customerId);
             Console.WriteLine("GetById: {0} {1}", customer.FirstName, customer.LastName);

             customer.LastName = "Chen";
             Update(customer);
             var updatedCustomer = GetById(customerId);
             Console.WriteLine("updated: {0} {1}", updatedCustomer.FirstName, updatedCustomer.LastName);

             Delete(customerId);
             var existedCustomer = GetById(customerId);
             Console.WriteLine("after deleted: existing: {0}", existedCustomer != null);

             Console.ReadLine();
         }

6. 完整的代码

 using NHibernate;
 using NHibernate.Cfg;
 using NHibernate.Dialect;
 using NHibernate.Driver;
 using System;
 using System.Collections.Generic;
 using System.Reflection;

 namespace NHibernateDemoApp
 {
     class Program
     {
         private static ISessionFactory _sessionFactory;

         public static ISessionFactory SessionFactory
         {
             get
             {
                 if (_sessionFactory == null)
                 {
                     var cfg = new Configuration();

                     cfg.DataBaseIntegration(x =>
                     {
                         x.ConnectionString = "Data Source=localhost;Initial Catalog=NHibernateDemoDB;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False;ApplicationIntent=ReadWrite;MultiSubnetFailover=False";
                         x.Driver<SqlClientDriver>();
                         x.Dialect<MsSql2008Dialect>();
                     });
                     cfg.AddAssembly(Assembly.GetExecutingAssembly());
                     _sessionFactory = cfg.BuildSessionFactory();
                 }
                 return _sessionFactory;
             }
         }

         static void Main(string[] args)
         {
             Customer newCustomer = CreateCustomer();
             int customerId = Insert(newCustomer);
             Console.WriteLine("new customer id: {0}", customerId);

             IList<Customer> list = GetAll();
             Console.WriteLine("customer list count: {0}", list.Count);
             foreach(var item in list)
             {
                 Console.WriteLine("{0} {1}", item.FirstName, item.LastName);
             }

             var customer = GetById(customerId);
             Console.WriteLine("GetById: {0} {1}", customer.FirstName, customer.LastName);

             customer.LastName = "Chen";
             Update(customer);
             var updatedCustomer = GetById(customerId);
             Console.WriteLine("updated: {0} {1}", updatedCustomer.FirstName, updatedCustomer.LastName);

             Delete(customerId);
             var existedCustomer = GetById(customerId);
             Console.WriteLine("after deleted: existing: {0}", existedCustomer != null);

             Console.ReadLine();
         }

         private static Customer CreateCustomer()
         {
             var customer = new Customer
             {
                 FirstName = "Daniel",
                 LastName = "Tang",
                 Points = ,
                 HasGoldStatus = true,
                 MemberSince = new DateTime(, , ),
                 CreditRating = CustomerCreditRating.Good,
                 AverageRating = 42.42424242,
                 Street = "123 Somewhere Avenue",
                 City = "Nowhere",
                 Province = "Alberta",
                 Country = "Canada"
             };

             return customer;
         }

         private static IList<Customer> GetAll()
         {
             using (var session = SessionFactory.OpenSession())
             {
                 IList<Customer> list = session.CreateCriteria<Customer>().List<Customer>();
                 return list;
             }
         }

         private static Customer GetById(int id)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 Customer customer = session.Get<Customer>(id);
                 return customer;
             }
         }

         private static int Insert(Customer customer)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 var identifier = session.Save(customer);
                 session.Flush();
                 return Convert.ToInt32(identifier);
             }
         }

         private static void Update(Customer customer)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 session.SaveOrUpdate(customer);
                 session.Flush();
             }
         }

         private static void Delete(int id)
         {
             using (var session = SessionFactory.OpenSession())
             {
                 var customer = session.Load<Customer>(id);
                 session.Delete(customer);
                 session.Flush();
             }
         }
     }
 }

7. 执行结果