.net - Fluent NHibernate Cascade 问题 - 尝试插入 NULL ID

Question

我有以下模型和映射(下面的代码片段)。

一场比赛从一开始就必须有多个与之相关的比赛答案(多项选择)。

目前，使用如下所示的 Fluent NHibernate 映射，当我创建一个全新的 Competition 对象，填充属性，然后创建 3 个全新的 CompetitionAnswer 对象并将它们添加到 CompetitionAnswers 属性(竞争属性)时，我希望调用 Save在将 1 Competition 行和 3 CompetitionAnswer 行插入数据库的 session 上。

但是，当我尝试在 session 中调用 Save 时，它​​会提示 CompetitionId 为 null，并且它无法将 null 插入到该字段的 CompetitionAnswers 表中 - 这是正确的，但它不应该，但是，我认为NHibernate 会先创建 Competition，然后在 CompetitionAnswers 表中使用新生成的 IDENTITY 值(CompetitionId)？

比赛(模特)

public virtual int CompetitionId { get; private set; }
public virtual string Title { get; set; }
public virtual string Description { get; set; }
public virtual IList<CompetitionAnswer> CompetitionAnswers { get; set; }

竞赛答案(模特)

public virtual int CompetitionAnswerId { get; set; }
public virtual string Answer { get; set; }
public virtual Competition Competition { get; set; }

CompetitionMap (Fluent NHibernate Mapping)

public CompetitionMap()
{
    Id(x => x.CompetitionId)
        .GeneratedBy.Native();
    Map(x => x.Title);
    Map(x => x.Description);
    HasMany(x => x.CompetitionAnswers)
        .Cascade.AllDeleteOrphan()
        .KeyColumn("CompetitionId")
        .Inverse();
    Table("Competitions");
}

CompetitionAnswerMap (Fluent NHibernate Mapping)

public CompetitionAnswerMap()
{
    Id(x => x.CompetitionAnswerId)
        .GeneratedBy.Native();
    Map(x => x.Answer);
    References(x => x.Competition)
        .Column("CompetitionId");
    Table("CompetitionAnswers");
}

这是我用来测试此场景的一些示例代码，它会生成错误:

Competition c = new Competition();

c.Description = "Description";
c.Title = "Title";

CompetitionAnswer a1 = new CompetitionAnswer { Answer = "Answer 1" };
CompetitionAnswer a2 = new CompetitionAnswer { Answer = "Answer 2" };
CompetitionAnswer a3 = new CompetitionAnswer { Answer = "Answer 3" };

c.CompetitionAnswers.Add(a1);
c.CompetitionAnswers.Add(a2);
c.CompetitionAnswers.Add(a3);

session.Save(c);

我一尝试保存就得到的确切错误是:

Cannot insert the value NULL into column 'CompetitionId', table 'CompetitionAnswers'; column does not allow nulls. INSERT fails. The statement has been terminated.

谁能解释一下为什么这目前不起作用？

Answer 1

References(x => x.Competition)
    .Column("CompetitionId")
    .Not.Nullable(); //add this

并且还要确保除了将 child 放在其集合中的 parent 之外， child 还指向 parent 。当父级为逆时，这是必需的。

a1.Competition = c; 

是那个栏目 non null在数据库端但在 NH 端映射为可为空？