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 = 100,
                HasGoldStatus = true,
                MemberSince = new DateTime(2012, 1, 1),
                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 = 100,
                HasGoldStatus = true,
                MemberSince = new DateTime(2012, 1, 1),
                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