c# nhibernate id 是否在删除时自动重置？

Question

我有一个关于使用 Nhibernate 删除实体的不一致（在我的程序中）的问题。

我必须存储实体和绑定它们的二元关系。

这是模型：

public interface IPersistent
{
    int ID { get ; set;}        
}

public virtual class Entity : IPersistent {
   //relations where the entity appears on the left side
   public ISet<Relation> LeftRelations  { get;}

   //relations where the entity appears on the right side
   public ISet<Relation> RightRelations { get;}       
}

public virtual class Relation : IPersistent {
   public Entity LeftEntity     { get;}
   public Entity RightEntity    { get;}
   public RelationType Type     { get;}

   // must be called before ISession.Delete()
   public void ClearRelation(){
        LeftEntity.LeftRelations.Remove(this);
        RightEntity.RightRelations.Remove(this);
        LeftEntity = null;
        RightEntity = null;
   }
}

我的映射看起来像：

<class name="Entity" table="entity">
    <id column="id_entity" name"ID" unsaved-value="-1" type=Int32>
        <generator class ="native">
            <param name ="sequence">seq_task_id_entity</param>
        </generator>
    </id>
     <set name="LeftRelations" table ="relation" generic="true"
          cascade="all" inverse="true">
         <key column="left_entity"  foreign-key="id_entity"/>
         <one-to-many class ="Relation"/>      
     </set>
     <set name="RightRelations" table ="relation" generic="true" 
          cascade="all" inverse="true">
       <key column ="right_entity"  foreign-key ="id_entity"/>
       <one-to-many class ="Relation"/>      
     </set>
</class>

<class name="Relation" table="relation" >
    <id column="id_relation" name"ID" unsaved-value="-1" type=Int32>
        <generator class ="native">
            <param name ="sequence">seq_task_id_relation</param>
        </generator>
    </id>
    <many-to-one name ="LeftEntity" class="Entity"  cascade="all" 
                    update="true" not-null="true">
          <column name ="left_entity" sql-type="integer" not-null ="true"></column>
    </many-to-one>

    <many-to-one name ="RightEntity" class ="Item" cascade="all" 
                    update="true" not-null="true">
          <column name ="right_entity" sql-type="integer" not-null ="true"></column>
     </many-to-one>   
</class>

我可以保留实体和关系实例。当我删除一个持久实体（未绑定到任何关系）时，其 ID 属性在提交后更新为未保存的值。但是当我删除持久关系时，数据库中的关系行被删除，但是关系'ID 属性没有重置为未保存的值。

这种行为正常吗？还是我的 nh 映射不正确？

Answer 1

要回答这个问题：

But when I delete a persisted relation, the relation row in database is deleted, but the relation'ID property is not resetted to the unsaved-value.

unsaved-value是用来比较的设置。不是设置值。

NHibernate 只需要这个设置来了解传递给 ISession 的实体是否应该被视为 Transient 或 Existing in DB。

The unsaved-value is just a constant setting - used just for comparison and decision: is object transient or existing.

文档：

5.1.4. id

<id
    name="PropertyName"                      (1)
    type="typename"                          (2)
    column="column_name"                     (3)
    unsaved-value="any|none|null|id_value"   (4)
    access="field|property|nosetter|ClassName(5)">
    ...

...
(4) unsaved-value (optional - defaults to a "sensible" value): An identifier property value that indicates that an instance is newly instantiated (unsaved), distinguishing it from transient instances that were saved or loaded in a previous session.

c# nhibernate id 是否在删除时自动重置？

c# nhibernate id automatically reset on delete or not?

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