NHibernate - 通过 id 或对象引用访问对象的父对象

Question

我有以下类：

public class Parent
{
    public virtual int ParentId { get; set; }
    public virtual string Name { get; set; }
    public virtual ICollection<Child> Children { get; set; }
}

public class Child
{
    public virtual int ChildId { get; set; }
    public virtual string Name { get; set; }
    //public virtual int ParentId { get; set; }
    public virtual Parent Parent { get; set; }
}

这些类以一对多关系映射到数据库中的相应表。在我的映射类中，我执行以下操作：

using FluentNHibernate.Mapping;
public partial class ParentMap : ClassMap<Parent>
{
    public ParentMap()
    {
        Id(p => p.ParentId).Column.("PARENT_ID").GeneratedBy.Native();
        Map(p => p.Name).Column("PARENT_NAME").Not.Nullable();
        HasMany<Child>(p => p.Children).Cascade.All().LazyLoad().Inverse().AsSet();
    }
}

public partial class ChildMap : ClassMap<Child>
{
    public ChildMap()
    {
        Id(c => c.ChildId).Column("CHILD_ID").GeneratedBy.Native();
        Map(c => c.Name).Column("CHILD_NAME").Not.Nullable();
        References<Parent>(c => x.Parent).Column("PARENT_ID").Not.LazyLoad().Not.Nullable();
    }
}

我需要做的是公开（取消注释上面的类定义中的行） Child 类中的 ParentId 属性，以便我可以执行以下操作：

var child = new Child();
child.ParentId = 1;

也就是说，我想要能够通过 child.ParentId 属性将 Parent 附加到 Child，同时仍然能够通过 child.Parent 属性访问 Parent。例如，

// i currently have to do the following in order to link the child with
// the parent when I update an existing Child instance (ParentService() and 
// ChildService() are service classes that sit between my applications and
// NHibernate).
var parentService = new ParentService();
var parent = parentService.GetById(1);
var child = new Child() { ChildId = 2, Parent = parent, Name = "New Name" };
var childService = new ChildService();
childService.Save(child);

// in a different project, i access the Parent object via the child's
// Parent property
var childService = new ChildService();
var child = childService.GetById(2);
Console.WriteLine(child.Parent.Name);


// i want to do this instead
var child = new Child() { Id = 2, ParentId = 1, Name = "New Name" };
var childService = new ChildService();
childService.Save(child);
Console.WriteLine(child.Id); // 11

// [ ... ]

var childService = new ChildService();
var child = childService.GetById(2);
Console.WriteLine(child.Parent.Name);

我将如何更改映射来实现这一点？ TIA，

拉尔夫·汤普森

Answer 1

这不是 NHibernate 的正确用法。

要获取父级的 Id，请使用：

var parentId = child.Parent.Id; //this does not cause loading

要通过 Id 设置父级，请使用

child.Parent = session.Load<Parent>(parentId); //this never goes to the DB either