NHibernate 先有个大概的理解

ORM是什么东西？复杂的名字叫对象关系模型。最常用的就是数据库到你的项目里的对象的映射,这样你可以像操作对象一样操作数据库，并且额外的好处是，如果你的语句比较兼容的话，可以更换数据库的时候减少很多工作。

NHibernate，是个什么东西？它其实不是个东西，是ORM在.NET上实现的一个功能性类库。

例子背景：

项目名称 NhibernateSample  数据库MSSQL2005 要用的表Student  字段

 [StudentId] [int] IDENTITY(1,1) NOT NULL,
 [StudentName] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL,
 [StudentPassword] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL,
 [EmailAddress] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL,
 [DateCreated] [nvarchar](50) COLLATE Chinese_PRC_CI_AS NULL,

第一步：

既然是个类库，得先下载下来,地址 http://nhforge.org/media/Default.aspx?Sort=Downloads&PageIndex=1,

版本多,这一点也是很麻烦的，很多东西版本太多，有时候选择多了反而不是好事。下载后得到 NHibernate-3.0.0.GA-bin.rar

最简单的办法就是把所有 .dll 都拷贝到你的bin文件里然后添加它们的引用,这就完成了对NHibernate使用的第一步。

第二步：写个Nhibernate连接数据库的XML文件hibernate.cfg.xml放到bin目录里，为什么是hibernate.cfg.xml这个名字呢？看啊，

NHibernate.Cfg.Configuration mCfg = new NHibernate.Cfg.Configuration().Configure();如果没这个文件这句会报错，说找不到hibernate.cfg.xml这个文件，那么为什么非要是这个名字呢？VS2008里右键点Configure[从元数据]得到

public const string DefaultHibernateCfgFileName = "hibernate.cfg.xml";
public const string MappingSchemaXMLNS = "urn:nhibernate-mapping-2.2";看见了吧，人家默认的给你定好了，有现成的就用现成的，只要好用。

hibernate.cfg.xml内容

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration  xmlns="urn:nhibernate-configuration-2.2" >
    <session-factory>
        <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
        <property name="connection.connection_string">
            Data Source=.;Initial Catalog=NHibernateSample;Persist Security Info=True;User ID=sa;Password=sa
        </property>
        <property name="adonet.batch_size">10</property>
        <property name="show_sql">true</property>
        <property name="dialect">NHibernate.Dialect.MsSql2000Dialect</property>
        <property name="use_outer_join">true</property>
        <property name="command_timeout">10</property>
        <property name="query.substitutions">true 1, false 0, yes 'Y', no 'N'</property>
        <property name='proxyfactory.factory_class'>NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property>
        <mapping assembly="NhibernateSample"/>
    </session-factory>
</hibernate-configuration>

注意这个config文件里的配置节点 xmlns="urn:nhibernate-configuration-2.2" ，人家也给你配好了，不能改成别的，和刚才那个名字一样，这就是配置文件的麻烦，很麻烦。

第三步：写表里字段的映射文件Student.cs和Student.hbm.xml，这两个文件可以用CodeSmith调用NHibernate模板生成，不过生成还得根据需要再改改。

Student.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace NhibernateSample
{
    public class Student
    {
        public Student() { }

        private int studentId;
        private string studentName;
        private string studentPassword;
        private string emailAddress;
        private string dateCreated;

        public virtual int StudentId
        {
            get { return studentId; }
            set { studentId = value; }
        }

        public virtual string StudentName
        {
            get { return studentName; }
            set { studentName = value; }
        }
        public virtual string StudentPassword
        {
            get { return studentPassword; }
            set { studentPassword = value; }
        }
        public virtual string EmailAddress
        {
            get { return emailAddress; }
            set { emailAddress = value; }
        }
        public virtual string DateCreated
        {
            get { return dateCreated; }
            set { dateCreated = value; }
        }
    }

}

Student.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="NhibernateSample.Student, NhibernateSample" table="Student">
    <id name="StudentId" column="StudentId" type="Int32">
      <generator class="native" />
    </id>
    <property name="StudentName" column= "StudentName" type="string" length="40"/>
    <property name="StudentPassword" type="string" length="20"/>
    <property name="EmailAddress" type="String" length="40"/>
    <property name="DateCreated" type="String" length="100"/>
  </class>
</hibernate-mapping>

第四步：简单调用

Dal.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using NHibernate;

namespace NhibernateSample
{
    public class Dal
    {
        public void testData()
        {

            NHibernate.Cfg.Configuration mCfg = new NHibernate.Cfg.Configuration().Configure();
            NHibernate.ISessionFactory SessionFactory = null;

            SessionFactory = mCfg.BuildSessionFactory();
            ISession vSession = SessionFactory.OpenSession();

            #region 查询

            string hsql = "from Student";
            IQuery query = vSession.CreateQuery(hsql);

            //this.dataGridView1.DataSource = query.List<Person>();   
            IList<Student> list = query.List<Student>();
            if (list.Count > 0)
            {
                Student obj = (Student)list[0];
                //.....   
            }

            #endregion

            #region 插入

            Student stu = new Student();
            stu.StudentName = "test22";
            stu.StudentPassword = "test22";
            stu.EmailAddress = "test22@54job.com";
            stu.DateCreated = "代替时间";
            ITransaction vTransaction = vSession.BeginTransaction();
            try
            {
                vSession.Save(stu);
                vTransaction.Commit();
            }
            catch (Exception)
            {
                vTransaction.Rollback();
            }
            vSession.Close();

            #endregion

            #region 更新
            /*  
            IQuery query = vSession.CreateQuery("from Student where StudentName='kexd'");  
            IList<Student> list = query.List<Student>();  
            ITransaction vTransaction = vSession.BeginTransaction();  
            try  
            {  
                foreach (Student stu in list)  
                {  
                    stu.EmailAddress = "kesfzu@21cn.com";  
                    vSession.Save(stu);  
                }  
                vTransaction.Commit();  
            }  
            catch (Exception)  
            {  
                vTransaction.Rollback();  
            }  
            finally  
            {  
                vSession.Close();  
            }  
             */
            #endregion

            #region 删除
            /*  
            IQuery query = vSession.CreateQuery("from Student where StudentName='ffer'");  
            IList<Student> list = query.List<Student>();  
            ITransaction vTransaction = vSession.BeginTransaction();  
            try  
            {  
                foreach (Student stu in list)  
                {  
                    vSession.Delete(stu);  
                }  
                vTransaction.Commit();  
            }  
            catch (Exception)  
            {  
                vTransaction.Rollback();  
            }  
            finally  
            {  
                vSession.Close();  
            }  
             */
            #endregion
        }
    }

}