NHibernate条件查询(Criteria Query)

代码

典型用法：从ISession接口中创建ICriteria实例对象；在这个ICriteria实例对象上设置一个或多个表达式；要求ICriteria接口返回需要的列表，就是根据表达式从数据库中返回对象。
1 .创建ICriteria实例
使用ISession接口的CreateCriteria方法创建了NHibernate.ICriteria接口一个特定的持久化类的查询实例，也可以说ISession是用来制造Criteria实例的工厂。
public  IList < Customer >  CreateCriteria()
{
    ICriteria crit  =  _session.CreateCriteria( typeof (Customer));
    crit.SetMaxResults( 50 );
    IList < Customer >  customers  =  crit.List < Customer > ();
     return  customers;
}
例如上面的例子返回Customer对象集合，设置最大的集合数量为50条。
2 .模糊查询
使用ICriteria接口提供的Add方法添加Restrictions类中约束表达式可以限制一些结果集的作用。
public  IList < Customer >  LikeAndBetween()
{
  IList < Customer >  customers  =      _session.CreateCriteria( typeof (Customer))
    .Add(Restrictions.Like( " Firstname " ,  " YJing% " ))
    .Add(Restrictions.Between( " Lastname " ,  " A% " ,  " Y% " ))
        .List < Customer > ();
     return  customers;
}
3 .结果集排序
使用ICriteria.Order对结果集排序，第二个参数true代表asc，false代表desc。例如下面例子查询Customer对象按FirstName降序、Lastname升序。
public  IList < Customer >  Order()
{
     return  _session.CreateCriteria( typeof (Customer))
        .Add(Restrictions.Like( " Firstname " , " Y% " ))
        .AddOrder( new  NHibernate.Criterion.Order( " Firstname " ,  false ))
        .AddOrder( new  NHibernate.Criterion.Order( " Lastname " ,  true ))
        .List < Customer > ();
}
4 .条件查询
   ///  利用CriteriaAPI获取顾客ID大于lId小于gId的顾客        public IList <Customer>  GreaterAndLetter(int lId,int gId)
 {
return  _session.CreateCriteria( typeof (Customer))
  .Add(Restrictions.Gt( " CustomerId " , lId)) // 大于
  .Add(Restrictions.Eq( " CustomerId " , lId)) // 等于
  .Add(Restrictions.Or(Restrictions.Eq( " CustomerId " , gId), Restrictions.Lt( " CustomerId " , gId))) // 小于等于
  .List < Customer > ();
}

测试：
[TestFixture]
     public   class  QueryCriteriaAPIFixture
    {
         private  SessionManager _helper;
         private  ISession _session;
         private  QueryCriteriaAPI _queryCriteriaAPI;
        [TestFixtureSetUp]
         public   void  TestFixtureSetup()
        {_helper  =   new  SessionManager();}
        [SetUp]
         public   void  Setup()
        {
            _session  =  _helper.GetSession();
            _queryCriteriaAPI  =   new  QueryCriteriaAPI(_session);
        }
 [Test]
public   void  CreateCriteriaTest()
{
IList < Customer >  customers  =  _queryCriteriaAPI.CreateCriteria();
   Assert.AreEqual( 5 , customers.Count);
 }
[Test]
public   void  LikeAndBetweenTest()
{
 IList < Customer >  customers  =  _queryCriteriaAPI. LikeAndBetween();
Assert.AreEqual( 1 , customers.Count);
}
 [Test]
  public   void  OrderTest()
 {
    IList < Customer >  customers  =  _queryCriteriaAPI.Order();
            Assert.AreEqual( 1 , customers.Count);
 }
[Test]
public   void  GreaterAndLetterTest()
{
     IList < Customer >  customers＝ _queryCriteriaAPI.GreaterAndLetter ( 1 , 4 );
       foreach  (Customer c  in  customers)
       {
         Assert.GreaterOrEqual(c.CustomerId,  1 ); // 大于等于
         Assert.LessOrEqual(c.CustomerId,  4 ); // 小于等于
       }
  }   
}

转载于:https://www.cnblogs.com/hubcarl/archive/2011/03/15/1706385.html