NHibernate - Linq

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在本章中，我们将介绍人们将使用的另一个常见 API 是 NHibernate LINQ 提供程序。它通过 ISession 上的扩展方法进行访问，签名是Query <T>。使用 LINQ 有两种语法 -

• 查询链接语法
• 查询理解语法

查询链接语法

您可以使用方法链语法访问数据库中的任何记录，如以下程序所示。

var customer = session.Query<Customer>() .Where(c => c.FirstName == "Laverne")

• 你可以看到我们有查询，还有 WHERE 子句，你可以有额外的 WHERE 子句和类似的 select 子句。

• 这是可以在普通 LINQ 中使用的标准方法链语法。

• LINQ to Objects 或 LINQ to SQL，您可能熟悉的任何其他 LINQ 提供程序。

让我们看一个简单的示例，在该示例中我们将检索名字为 Laverne 的客户。现在，我们可能有多个名字为 Laverne 的客户，因此我们将仅检索第一个客户。

using System; 
using System.Data; 
using System.Linq; 
using System.Reflection; 

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Criterion; 
using NHibernate.Dialect; 
using NHibernate.Driver; 
using NHibernate.Linq;

namespace NHibernateDemo { 

   internal class Program {
	
      private static void Main() { 
		
         var cfg = ConfigureNHibernate(); 
         var sessionFactory = cfg.BuildSessionFactory();
         using(var session = sessionFactory.OpenSession()) 
         
         using(var tx = session.BeginTransaction()) {
            var customer = session.Query<Customer>() 
               .Where(c => c.FirstName == "Laverne").First(); 
            Console.WriteLine(customer); 
            tx.Commit(); 
         }
			
         Console.WriteLine("Press <ENTER> to exit..."); 
         Console.ReadLine(); 
      }
		
      private static Configuration ConfigureNHibernate() { 
		
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration(); 
         
         cfg.DataBaseIntegration(x => { 
            x.ConnectionStringName = "default"; 
            x.Driver<SqlClientDriver>(); 
            x.Dialect<MsSql2008Dialect>(); 
            x.IsolationLevel = IsolationLevel.RepeatableRead; 
            x.Timeout = 10; 
            x.BatchSize = 10; 
         }); 
         
         cfg.SessionFactory().GenerateStatistics();
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         return cfg; 
      } 
   } 
}

现在，当上面的代码被编译并执行时，您将看到以下输出。

Laverne Hegmann (4e97c816-6bce-11e1-b095-6cf049ee52be)
   Points: 74
   HasGoldStatus: True
   MemberSince: 4/4/2009 12:00:00 AM (Utc)
   CreditRating: Neutral
   AverageRating: 0

   Orders:
      Order Id: 4ea14d96-6bce-11e1-b095-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b096-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b097-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b098-6cf049ee52be
		
Press <ENTER> to exit...

查询理解语法

还有查询理解语法，它看起来更像是使用 from、where 和 select 关键字的 SQL。

因此，让我们看一下同一个示例，但这次我们使用 LINQ 推导式语法，它看起来更像 SQL，如以下程序所示。

using System; 
using System.Data; 
using System.Linq; 
using System.Reflection; 

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Criterion; 
using NHibernate.Dialect; 
using NHibernate.Driver; 
using NHibernate.Linq;

namespace NHibernateDemo { 

   internal class Program { 
	
      private static void Main() { 
		
         var cfg = ConfigureNHibernate(); 
         var sessionFactory = cfg.BuildSessionFactory();
         using(var session = sessionFactory.OpenSession()) 
         
         using(var tx = session.BeginTransaction()) {
            var customer = (from c in session.Query<Customer>() 
               where c.FirstName == "Laverne" select c).First();
            Console.WriteLine(customer); 
            tx.Commit();
         }
         
         Console.WriteLine("Press <ENTER> to exit..."); 
         Console.ReadLine(); 
      }
      
      private static Configuration ConfigureNHibernate() {
		
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration(); 
         
         cfg.DataBaseIntegration(x => { 
            x.ConnectionStringName = "default"; 
            x.Driver<SqlClientDriver>(); 
            x.Dialect<MsSql2008Dialect>(); 
            x.IsolationLevel = IsolationLevel.RepeatableRead; 
            x.Timeout = 10; 
            x.BatchSize = 10; 
         }); 
         
         cfg.SessionFactory().GenerateStatistics();
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         return cfg; 
      } 
   } 
}

现在让我们再次运行该应用程序，您将看到以下输出。

Laverne Hegmann (4e97c816-6bce-11e1-b095-6cf049ee52be)
   Points: 74
   HasGoldStatus: True
   MemberSince: 4/4/2009 12:00:00 AM (Utc)
   CreditRating: Neutral
   AverageRating: 0

   Orders:
      Order Id: 4ea14d96-6bce-11e1-b095-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b096-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b097-6cf049ee52be
      Order Id: 4ea14d96-6bce-11e1-b098-6cf049ee52be
		
Press <ENTER> to exit...

让我们看一下另一个示例，在该示例中我们将检索所有名字以字母 H 开头的客户。

using System; 
using System.Data; 
using System.Linq; 
using System.Reflection; 

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Criterion; 
using NHibernate.Dialect; 
using NHibernate.Driver; 
using NHibernate.Linq;

namespace NHibernateDemo { 

   internal class Program { 
	
      private static void Main() { 
		
         var cfg = ConfigureNHibernate(); 
         var sessionFactory = cfg.BuildSessionFactory();
         using(var session = sessionFactory.OpenSession()) 
         
         using(var tx = session.BeginTransaction()) {
            var customers = session.Query<Customer>() .Where(c =<
               c.FirstName.StartsWith("H"));
            
            foreach (var customer in customers.ToList()) { 
               Console.WriteLine(customer); 
            }
				
            tx.Commit(); 
         }
			
         Console.WriteLine("Press <ENTER> to exit..."); 
         Console.ReadLine(); 
      }
		
      private static Configuration ConfigureNHibernate() { 
		
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration(); 
         
         cfg.DataBaseIntegration(x => { 
            x.ConnectionStringName = "default"; 
            x.Driver<SqlClientDriver>(); 
            x.Dialect<MsSql2008Dialect>(); 
            x.IsolationLevel = IsolationLevel.RepeatableRead; 
            x.Timeout = 10; 
            x.BatchSize = 10; 
         }); 
			
         cfg.SessionFactory().GenerateStatistics();
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         return cfg; 
      } 
   } 
}

同样，查询理解语法将类似于以下程序。

using System; 
using System.Data; 
using System.Linq; 
using System.Reflection; 

using HibernatingRhinos.Profiler.Appender.NHibernate; 
using NHibernate.Cfg; 
using NHibernate.Criterion; 
using NHibernate.Dialect; 
using NHibernate.Driver; 
using NHibernate.Linq;

namespace NHibernateDemo { 

   internal class Program { 
	
      private static void Main() { 
		
         var cfg = ConfigureNHibernate(); 
         var sessionFactory = cfg.BuildSessionFactory();
         using(var session = sessionFactory.OpenSession()) 
         
         using(var tx = session.BeginTransaction()) {
            var customers = from c in session.Query<Customer>() 
               where c.FirstName.StartsWith("H") select c;
            
            foreach (var customer in customers.ToList()) { 
               Console.WriteLine(customer); 
            }
				
            tx.Commit(); 
         }
			
         Console.WriteLine("Press <ENTER> to exit..."); 
         Console.ReadLine(); 
      }
		
      private static Configuration ConfigureNHibernate() { 
		
         NHibernateProfiler.Initialize(); 
         var cfg = new Configuration(); 
         
         cfg.DataBaseIntegration(x => { 
            x.ConnectionStringName = "default"; 
            x.Driver<SqlClientDriver>(); 
            x.Dialect<MsSql2008Dialect>(); 
            x.IsolationLevel = IsolationLevel.RepeatableRead; 
            x.Timeout = 10; 
            x.BatchSize = 10; 
         }); 
			
         cfg.SessionFactory().GenerateStatistics();
         cfg.AddAssembly(Assembly.GetExecutingAssembly()); 
         return cfg; 
      } 
   }  
}

让我们再次运行这个应用程序，您将看到所有名字以字母 H 开头的客户。

Herman Crooks (4ead3480-6bce-11e1-b15c-6cf049ee52be)
   Points: 74
   HasGoldStatus: True
   MemberSince: 12/3/2010 12:00:00 AM (Utc)
   CreditRating: Neutral
   AverageRating: 0

   Orders:
      Order Id: 4ead3480-6bce-11e1-b15d-6cf049ee52be
      Order Id: 4ead3480-6bce-11e1-b15e-6cf049ee52be
      Order Id: 4ead3480-6bce-11e1-b15f-6cf049ee52be
      Order Id: 4ead3480-6bce-11e1-b160-6cf049ee52be
      Order Id: 4ead3480-6bce-11e1-b161-6cf049ee52be
      Order Id: 4ead3480-6bce-11e1-b162-6cf049ee52be
      Order Id: 4ead3480-6bce-11e1-b163-6cf049ee52be

Hudson Bins (4ec03f80-6bce-11e1-b2b7-6cf049ee52be)
   Points: 56
   HasGoldStatus: False
   MemberSince: 10/20/2008 12:00:00 AM (Utc)
   CreditRating: Terrible
   AverageRating: 0

   Orders:
      Order Id: 4ec03f80-6bce-11e1-b2b8-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2b9-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2ba-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2bb-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2bc-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2bd-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2be-6cf049ee52be
      Order Id: 4ec03f80-6bce-11e1-b2bf-6cf049ee52be

Hettie Feest (4ec50240-6bce-11e1-b300-6cf049ee52be)
   Points: 82
   HasGoldStatus: False
   MemberSince: 4/10/2009 12:00:00 AM (Utc)
   CreditRating: Neutral
   AverageRating: 0

   Orders:
      Order Id: 4ec50240-6bce-11e1-b301-6cf049ee52be
      Order Id: 4ec50240-6bce-11e1-b302-6cf049ee52be
      Order Id: 4ec50240-6bce-11e1-b303-6cf049ee52be
		
Press <ENTER> to exit...