流利的NHibernate一对多映射 [英] Fluent NHibernate One-To-Many Mapping

问题描述

我有以下两类：

广告

  public virtual int Id {get;组; 
公共虚拟IList< AdvertImage> AdvertImages {get;组; } 
  

AdvertImage

  public virtual int Id {get;组; } 
公共虚拟字符串Filename {get;组; 
 public virtual Advert Advert {get;组;在DB中，我的AdvertImages表具有与广告表相关的FKAdvertId有一个Id的PK。
 
 
这是一个一对多的映射，因为一个广告可以有很多的图像。
 
 
我的流利的NHibernate映射（为简洁起见）是：
 $ b $ p  AdvertMap  
  Id（x => x.Id）
 .GeneratedBy.Identity（）; 
 ... 
 HasMany（x => x.AdvertImages）
 .KeyColumn（AdvertId）
 .Inverse（）; 
 ... 
表（广告）; 
  
 
 
  AdvertImageMap   
 
  Id（x => x.Id）
 .GeneratedBy.Identity（）; 
 ... 
引用（x => x.Advert）
 .Column（AdvertId）; 
 ... 
表（AdvertImages）; 
  
我正在创建一个新的实例然后用 List< AdvertImage> 。
 $填充 AdvertImages 属性（Advert） b 
 $ b 
当我将我的广告对象保存到数据库时，我想将AdvertImages插入到他们的AdvertImages表中，对于两个表之间的关系，我需要首先发生Advert插入，以便生成PK Id，然后可以将其插入到AdvertImages表中。 （当我创建AdvertImage的列表时，我填充了Filename属性，但显然在该阶段没有新的AdvertId，所以当广告被持久化到DB时要填充）。 b 
 $ b 
我尝试过使用不同的Inverse（）和Cascade设置，但还没有成功。任何人都可以帮忙吗？
 
解决方案
您需要更改您的广告映射级联： 
 
 
  Id（x => x.Id）
 .GeneratedBy.Identity（）; 
 
 HasMany（x => x.AdvertImages）
 .KeyColumn（AdvertId）
 .Inverse（）
 .Cascade.AllDeleteOrphan（）; 
 
表格（广告）; 
  
然后，您应该可以做这样的事情来坚持一个 Advert 对象，它是子元素 AdvertImage 。
  Advert newAdvert = new Advert（）; 
 AdvertImage newImage = new AdvertImage（）; 
 newImage.Advert = newAdvert; 
 newAdvert.AdvertImages.Add（newImage）; 
 
 using（NHibernate.ISession session = SessionFactory.GetCurrentSession（））
 {
 using（NHibernate.ITransaction tran = session.BeginTransaction（））
 {
 session.Save（newAdvert）; 
 tran.Commit（）; 
 
 
 
 
 $ b我的实体通常包含用于双向的Add和Remove方法到这样的许多关系：
 
 
  public class Advert 
 {
 public virtual IList< AdvertImage> AdvertImages {get;组; } 
 
 public virtual void AddImage（AdvertImage newImage）
 {
 newImage.Advert = this; 
 AdvertImages.Add（newImage）; 
} 
} 
  
 
I have the following 2 classes:

Advert  
public virtual int Id { get; set;
public virtual IList<AdvertImage> AdvertImages { get; set; }
AdvertImage  
public virtual int Id { get; set; }
public virtual string Filename { get; set;
public virtual Advert Advert { get; set; }
In the DB, my AdvertImages table has the FK 'AdvertId' which relates to the Adverts table which has the PK of 'Id'.

This is a One-To-Many mapping, in that one advert can have many images.

My Fluent NHibernate mappings (edited for brevity) are:

AdvertMap  
Id(x => x.Id)
  .GeneratedBy.Identity();
...
HasMany(x => x.AdvertImages)
  .KeyColumn("AdvertId")
  .Inverse();
...
Table("Adverts");
AdvertImageMap  
Id(x => x.Id)
  .GeneratedBy.Identity();
...
References(x => x.Advert)
  .Column("AdvertId");
...
Table("AdvertImages");
I am creating a new instance of Advert in code, then populating the AdvertImages property (of Advert) with a List<AdvertImage>.

When I go to persist my Advert object to the DB, I would like the AdvertImages to be inserted into their AdvertImages table, but due to the relationship between the 2 tables, I need the Advert insertion to happen first, so as the PK Id is generated, which can then be inserted in the AdvertImages table. (When I create my list of AdvertImage, I am populating the Filename property, but obviously don't have the new AdvertId at that stage, so want that to be populated when the advert is persisted to the DB).

I have tried experimenting with different Inverse() and Cascade settings but haven't succeeded yet. Can anyone help please?
解决方案
You need to change your Advert mapping to cascade:
Id(x => x.Id)
  .GeneratedBy.Identity();

HasMany(x => x.AdvertImages)
  .KeyColumn("AdvertId")
  .Inverse()
  .Cascade.AllDeleteOrphan();

Table("Adverts");
You should then be able to do something like this to persist an Advert object and it's children AdvertImage.
Advert newAdvert = new Advert();
AdvertImage newImage = new AdvertImage();
newImage.Advert = newAdvert;
newAdvert.AdvertImages.Add(newImage);

using(NHibernate.ISession session = SessionFactory.GetCurrentSession())
{
    using (NHibernate.ITransaction tran = session.BeginTransaction())
    {
        session.Save(newAdvert);
        tran.Commit();
    }
}
My entities usually contain Add and Remove methods for bidirectional one to many relationships like this:
public class Advert
{
    public virtual IList<AdvertImage> AdvertImages { get; set; }

    public virtual void AddImage(AdvertImage newImage)
    {
        newImage.Advert = this;
        AdvertImages.Add(newImage);
    }
}


                        
这篇关于流利的NHibernate一对多映射的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！