MySQL + Entity Framework : Can't delete object

Question

我正在尝试通过 Entity Framework (MySQL/Connector) 删除具有外键关系的对象。

ClientAccount>>> ClientEmailAddresses

  foreach (ClientAccount client in recsClientStore.Deleted) {   
        ClientAccount stub = new ClientAccount();
        stub.Id = client.Id;
        this.DBContext.AttachTo("ClientAccounts", stub);


        stub.FkClientEmailAddresses.Clear();
        this.DBContext.DeleteObject(stub);
    }

    this.DBContext.SaveChanges();

.. 但是当我这样做时，出现以下错误:

The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.

我不太确定这会把我留在哪里。我必须先删除 EmailAddress 对象吗？我们对打开级联持谨慎态度，但它看起来越来越像需要整理外键。

Answer 1

问题在于:

stub.FkClientEmailAddresses.Clear();

不删除关系。它只将相关实体中的 FK 设置为 null。如果你想让它们真正删除，你必须:

• 通过在它们的对象集上调用 Remove 来删除它们
• 更改与 identifying relationship 的关系- 这将使 Clear 按预期工作
• 在 EDMX 和数据库中正确设置级联删除，根本不调用 Clear