NHibernate中的映射错误 [英] Mapping Error in NHibernate

问题描述

我正在尝试使用NHibernate连接到Northwind数据库.但是由于某种原因，我无法加载实体类型.

I am trying to use NHibernate to connect to a Northwind database. But for some reason, I am not able to load the Entity Type.

这是我的Entity类

This is my Entity class

public class Product
    {
        public virtual Int32 ProductId { get; set; }
        public virtual String Desc { get; set; }
    }

这是我的地图

 <class name="Product" table="Products">
    <id name="ProductId" column="ProductId" type="Int32">
      <generator class="identity"></generator>
    </id>
    <property name="Desc" column="ProductName" type="String" length="60">
    </property>
  </class>

我收到以下错误消息

无法加载实体:[OracleLinq.Product#12] [SQL:选择product0_.ProductId作为ProductId0_0_，product0_.ProductName作为ProductN2_0_0_ FROM产品product0_ WHERE product0_.ProductId =?]

could not load an entity: [OracleLinq.Product#12][SQL: SELECT product0_.ProductId as ProductId0_0_, product0_.ProductName as ProductN2_0_0_ FROM Products product0_ WHERE product0_.ProductId=?]

这是堆栈跟踪

   at NHibernate.Loader.Loader.LoadEntity(ISessionImplementor session, Object id, IType identifierType, Object optionalObject, String optionalEntityName, Object optionalIdentifier, IEntityPersister persister)
   at NHibernate.Loader.Entity.AbstractEntityLoader.Load(ISessionImplementor session, Object id, Object optionalObject, Object optionalId)
   at NHibernate.Loader.Entity.AbstractEntityLoader.Load(Object id, Object optionalObject, ISessionImplementor session)
   at NHibernate.Persister.Entity.AbstractEntityPersister.Load(Object id, Object optionalObject, LockMode lockMode, ISessionImplementor session)
   at NHibernate.Event.Default.DefaultLoadEventListener.LoadFromDatasource(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
   at NHibernate.Event.Default.DefaultLoadEventListener.DoLoad(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
   at NHibernate.Event.Default.DefaultLoadEventListener.Load(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options)
   at NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType)
   at NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType)
   at NHibernate.Impl.SessionImpl.ImmediateLoad(String entityName, Object id)
   at NHibernate.Proxy.AbstractLazyInitializer.Initialize()
   at NHibernate.Proxy.AbstractLazyInitializer.GetImplementation()
   at NHibernate.Proxy.Poco.Castle.CastleLazyInitializer.Intercept(IInvocation invocation)
   at Castle.DynamicProxy.AbstractInvocation.Proceed()
   at ProductProxy4c67cf5bf6e640ab82d8c21a90e2a62b.set_Desc(String value)
   at OracleLinq.Form1.Form1_Load(Object sender, EventArgs e)

我做错什么了吗?

推荐答案

第二次尝试:

这是您的注释中的配置，只是为了提高可读性:

Here is you configuration from your comments, just for readability:

Configuration cfg = new Configuration(); 
cfg.Configure(); 
cfg.AddAssembly(typeof(Product).Assembly); 
ISessionFactory sessionFactory = cfg.BuildSessionFactory(); 

IDbConnection conn = new SqlConnection(@"Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI;"); 
ISession session = sessionFactory.OpenSession(conn); 

Product product = (Product)session.Load(typeof(Product), 12); 
product.Desc = "";

很明显，NHibernate具有映射文件，它无法生成查询.

It's clear that NHibernate has the mapping file, it could not have generated the query.

可能是那个

• 数据库不存在:您已经检查了此内容.
• 表不存在:打开一个sql控制台(使用相同的连接字符串)，然后将错误消息中的sql复制粘贴到该表中.能行吗?
• 连接未打开:请参见bollow

• the database is not there : you already checked this.
• the table is not there : open a sql console (using the same connect string) and copy-paste the sql from the error message into it. Does it work?
• the connection is not opened : see bollow

我认为您需要自己打开连接.更好的是，让NHibernate创建和管理连接.

I think that you need to open the connection yourself. Even better you let NHibernate create and manage the connections.

尝试一下:

Configuration cfg = new Configuration(); 
cfg.Configure(); 
cfg.AddAssembly(typeof(Product).Assembly); 
ISessionFactory sessionFactory = cfg.BuildSessionFactory(); 

ISession session = sessionFactory.OpenSession(); 

Product product = (Product)session.Load(typeof(Product), 12); 
product.Desc = "";

连接字符串转到nhibernate.cfg.xml

the connectstring goes to the nhibernate.cfg.xml

<property name="connection.provider">NHibernate.Connection.DriverConnectionProvider, NHibernate</property>
<property name="connection.connection_string">
 Data Source=(local);Initial Catalog=Northwind;Integrated Security=SSPI;
</property>
<property name="dialect">NHibernate.Dialect.MsSql2000Dialect</property>

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