Delete抛出“Delete object would by cascade”

Question

我有以下模型：

<class name="Person" table="Person" optimistic-lock="version">
  <id name="Id" type="Int32" unsaved-value="0">
    <generator class="native" />
  </id>
  <!-- plus some properties here -->
</class>

<class name="Event" table="Event" optimistic-lock="version">
  <id name="Id" type="Int32" unsaved-value="0">
    <generator class="native" />
  </id>
  <!-- plus some properties here -->
</class>

<class name="PersonEventRegistration" table="PersonEventRegistration" optimistic-lock="version">
  <id name="Id" type="Int32" unsaved-value="0">
    <generator class="native" />
  </id>
  <property name="IsComplete" type="Boolean" not-null="true" />
  <property name="RegistrationDate" type="DateTime" not-null="true" />
  <many-to-one name="Person" class="Person" column="PersonId" foreign-key="FK_PersonEvent_PersonId" cascade="all-delete-orphan" />
  <many-to-one name="Event" class="Event" column="EventId" foreign-key="FK_PersonEvent_EventId" cascade="all-delete-orphan" />
</class>

在Person和Event中都没有指向PersonEventRegistration的属性。

当我试图从PersonEventRegistration中删除一个条目时，我得到了以下错误：

"deleted object would be re-saved by cascade"

问题是，我没有将这个对象存储在任何其他集合中-删除代码看起来像这样：

public bool UnregisterFromEvent(Person person, Event entry)
{
    var registrationEntry = this.session
        .CreateCriteria<PersonEventRegistration>()
        .Add(Restrictions.Eq("Person", person))
        .Add(Restrictions.Eq("Event", entry))
        .Add(Restrictions.Eq("IsComplete", false))
        .UniqueResult<PersonEventRegistration>();

    bool result = false;
    if (null != registrationEntry)
    {
        using (ITransaction tx = this.session.BeginTransaction())
        {
            this.session.Delete(registrationEntry);
            tx.Commit();
            result = true;
        }
    }
    return result;
}

我在这里做错了什么？

Answer 1

据我所知，cascade="all-delete-orphan"属于集合映射元素，而不是many-to-one。您还没有显示映射的其他两个部分，所以我不能肯定，但这可能(很可能)是问题所在。

我认为Person应该看起来像这样：

<!-- other properties -->
<set name="Events" inverse="true" cascade="all-delete-orphan">
    <key column="Person_id" />
    <one-to-many class="PersonEventRegistration" />
</set>

Event

<!-- similar mapping for Event -->

PersonEventRegistration

<!-- other properties -->
<many-to-one name="Person" class="Person" column="PersonId" foreign-key="FK_PersonEvent_PersonId" cascade="delete" <!-- or many ="all" ? --> />

实际上，以上可能是相互冲突的级联(这可能就是您所拥有的)。所以真的，我的答案是两件事：

1. cascade="all-delete-orphan"在many-to-one.
2. Make上没有任何意义确信你已经真正考虑过如何处理你的实体以及他们应该如何级联他们的操作。

Answer 2

尝试在删除操作中取消引用人员和事件：

    public bool UnregisterFromEvent(Person person, Event entry)
    {
        var registrationEntry = this.session
            .CreateCriteria<PersonEventRegistration>()
            .Add(Restrictions.Eq("Person", person))
            .Add(Restrictions.Eq("Event", entry))
            .Add(Restrictions.Eq("IsComplete", false))
            .UniqueResult<PersonEventRegistration>();

        bool result = false;
        if (null != registrationEntry)
        {
            using (ITransaction tx = this.session.BeginTransaction())
            {
                registrationEntry.Person = null;
                registrationEntry.Event = null;
                this.session.Delete(registrationEntry);
                tx.Commit();
                result = true;
            }
        }
        return result;
    }

另外，我没有意识到你可以添加对对象的限制，我会使用别名和I来写这篇文章。

            .Add(Restrictions.Eq("Person", person))
            .Add(Restrictions.Eq("Event", entry))