Fluent映射:使用联接表和级联

当前无法映射下表设置:

               Shop
             [1]  [1]                 
            /       \
          [n]       [n]
   Category-[m]---[n]-Article

行为应如下:
1-删除商店时,应删除所有文章和类别
2-删除类别时,应取消分配相关文章,但不能删除。
3-删除文章时,应取消分配相关类别,但不能删除。

public class ShopMap: ClassMap<Shop>
{
    public ShopMap()
    {
        this.Table("shop");
        Id(x => x.Id).Column("id").GeneratedBy.Native();
        Map(x => x.Name).Column("name");

        HasMany(x => x.Categories).Cascade.AllDeleteOrphan;
        HasMany(x => x.Articles).Cascade.AllDeleteOrphan;
    }
}

public class CategoryMap: ClassMap<Category>
{
    public CategoryMap()
    {
        this.Table("category");
        Id(x => x.Id).Column("id").GeneratedBy.Native();
        Map(x => x.Name).Column("name");

        References(x => x.Shop);

        HasManyToMany(x => x.Articles).Cascade.AllDeleteOrphan()
                                    .Table("article_category")
                                    .ChildKeyColumn("article_id")
                                    .ParentKeyColumn("category_id")
                                        .Inverse();
    }
}

public class ArticleMap: ClassMap<Article>
{
    public ArticleMap()
    {
        this.Table("article");
        Id(x => x.Id).Column("id").GeneratedBy.Native();
        Map(x => x.Name).Column("name");

        References(x => x.Shop);

        HasManyToMany(x => x.Categories).Cascade.All()
                                    .Table("article_category")
                                    .ParentKeyColumn("article_id")
                                    .ChildKeyColumn("category_id");
    }
}