NHibernate 映射 - 自引用：父母和孩子答案

【问题标题】：NHibernate mapping - self referencing: parent and childrenNHibernate 映射 - 自引用：父母和孩子
【发布时间】：2014-08-22 22:11:33
【问题描述】：

我正在尝试拥有这种模型：

public class Activity
{
    public virtual int ID { get; set; }

    public virtual int? ParentID { get; set; }
    public virtual int? RootID { get; set; }

    public virtual Activity Parent { get; set; }
    public virtual Activity Root { get; set; }
    public virtual IList<Activity> Children { get; set; }
}

如果你从结构的角度来看它，它就是一棵树。根元素没有父元素或根元素，但可能有子元素。它的任何子节点都必须有父节点和根节点（对于第一级子节点，根 = 父节点）

映射器是这样的：

public class ActivityMap : ClassMapping<Activity>
{
    public ActivityMap()
    {
        Table("activity");
        Lazy(true);
        Id(x => x.ID, map => map.Generator(Generators.Identity));

        ManyToOne(x => x.Root, map => { map.Column("RootID"); map.Cascade(Cascade.All); });

        Bag(x => x.Children,
           mapping =>
           {
               mapping.Inverse(false);
               mapping.Lazy(CollectionLazy.Lazy);
               mapping.Key(k => k.Column("ParentID"));
               mapping.Cascade(Cascade.All);
           },
           mapping => mapping.ManyToMany(map=>map.Class(typeof(Activity)))
           );
    }
}

问题是当我尝试获取孩子时，sql语句看起来像：

SELECT children0_.ParentID as ParentID1_,
children0_.elt as elt1_, 
activity1_.ID as ID55_0_, 
activity1_.TaskID as TaskID55_0_, 
activity1_.ActivityTypeID as Activity3_55_0_, 
activity1_.StateID as StateID55_0_, 
activity1_.Continueforward as Continue5_55_0_, 
activity1_.Ordernumber as Ordernum6_55_0_, 
activity1_.IsDeleted as IsDeleted55_0_, 
activity1_.Created as Created55_0_, 
activity1_.Modified as Modified55_0_, 
activity1_.StartTime as StartTime55_0_, 
activity1_.EndTime as EndTime55_0_, 
activity1_.Progress as Progress55_0_, 
activity1_.RootID as RootID55_0_ 
FROM Children children0_ left outer join activity activity1_ on children0_.elt=activity1_.ID WHERE children0_.ParentID=?

首先，它似乎在寻找不存在的 Children 表。应该是活动表
第二：我不确定那个“elt”列是什么......它在任何地方都不存在

有人知道如何制作这个映射吗？

后期编辑： 在回答第二个问题时发现： NHibernate elt field

【问题讨论】：

标签： nhibernate tree self bag

【解决方案1】：

在我以后的编辑中，我得到了第二个问题的答案。

对于第二个问题，我找到的解决方案是放弃与根实体的关系

ManyToOne(x => x.Root, map => { map.Column("RootID"); map.Cascade(Cascade.All); });

替换成

Property(x => x.RootID);

因为我不需要根的整个实体。我也为这样的儿童换过包：

Bag(x => x.Children,
           mapping =>
           {
               mapping.Inverse(false);
               mapping.Lazy(CollectionLazy.Lazy);
               mapping.Key(k => k.Column("ParentID"));
               mapping.Cascade(Cascade.All);
           },
           mapping => mapping.OneToMany()
           );

【讨论】：