选择性地禁用多对多链接表上的级联删除 [英] Selectively Disabling Cascade Delete on Many-to-Many Link Table

问题描述

是否可以在Entity Framework 5 Code First中的自动生成的多对多链接表上选择性删除级联删除选项？这是一个需要它的简单例子：

Is it possible to selectively remove the Cascade Delete option on an automatically-generated many-to-many link table in Entity Framework 5 Code First? Here's a simple example which needs it:

public class Parent
{
    public int Id { get; set; }

    public virtual IList<ChildA> As { get; set; }
    public virtual IList<ChildB> Bs { get; set; }
}

public class ChildA
{
    public int Id { get; set; }
    [Required]
    public virtual Parent Parent { get; set; }

    public virtual IList<ChildB> ChildBJoins { get; set; }
}

public class ChildB
{
    public int Id { get; set; }
    [Required]
    public virtual Parent Parent { get; set; }

    public virtual IList<ChildA> ChildAJoins { get; set; }
}

public class TestContext : DbContext
{
    public DbSet<Parent> Parents { get; set; }
    public DbSet<ChildA> As { get; set; }
    public DbSet<ChildB> Bs { get; set; }
}

当前窗体中的上下文将不适用于数据库，因为级联删除选项在链接表中引入。如果我要创建一个手动链接表，我可以使用Fluent API来配置它的一面，而不是级联，但该选项在多对多关系中是不可用的。

This context in its current form will not apply to a database because of the cascade delete option introduced on the link table. If I were to create a manual link table, I could use the Fluent API to configure one side of it to not cascade, but the option isn't available on a many-to-many relationship.

我知道我可以通过删除 ManyToManyCascadeDeleteConvention 根据这个问题，但这不是我之后 - 我只是希望能够做一个关系，或理想的一个关系的一边。

I'm aware that I can disable Cascade Deletes on all Many-to-Many joins by removing the ManyToManyCascadeDeleteConvention as per this question, but that's not what I'm after - I just want to be able to do it for one relationship, or ideally one side of one relationsip.

推荐答案

我怀疑在EntityTypeConfiguration映射类中没有办法，但是通过更改DbMigration类中的Up（）方法中的代码来实现。

I suspect there is no way to do it in an EntityTypeConfiguration mapping class, but I did it by changing the code in the Up() method in the DbMigration class.

生成的代码链接表是：

CreateTable(
    "dbo.ChildBChildAs",
    c => new
        {
            ChildB_Id = c.Int(nullable: false),
            ChildA_Id = c.Int(nullable: false),
        })
    .PrimaryKey(t => new { t.ChildB_Id, t.ChildA_Id })
    .ForeignKey("dbo.ChildBs", t => t.ChildB_Id, cascadeDelete: true)
    .ForeignKey("dbo.ChildAs", t => t.ChildA_Id, cascadeDelete: true)
    .Index(t => t.ChildB_Id)
    .Index(t => t.ChildA_Id);

您应该可以通过更改不想级联为false的方式使其正常工作：

You should be able to get it working by changing the side you don't want to cascade to false:

    .ForeignKey("dbo.ChildAs", t => t.ChildA_Id, cascadeDelete: false)

如果您可以使用FluentAPI做一次即可使用一对多，但我避风港没有办法找到一种办法。

It would be nice if you could do it using the FluentAPI as you can with one-to-many, but I haven't managed to find a way to do it

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