EF4.1 代码优先:如何为依赖实体中没有导航属性的关系禁用删除级联

EF4.1 Code First : How to disable delete cascade for a relationship without navigation property in dependent entity(EF4.1 代码优先:如何为依赖实体中没有导航属性的关系禁用删除级联)

问题描述

假设我有这两个非常基本的实体:

Let's say I have these two very basic entities:

public class ParentEntity
{
   public int Id;
   public virtual ICollection<ChildEntity> Childrens;
}

public class ChildEntity
{
   public int Id;
   public int ParentEntityId; // Foreign Key
   public virtual ParentEntity parent; // [NOTWANTED]
}

出于某些原因，我不希望 ChildEntity 保留对其父级的引用.我只希望它保留 ParentEntity id，仅此而已.到目前为止，没问题，我只是删除了 [NOTWANTED] 行，一切正常.

For some reasons, I don't want the ChildEntity to hold a reference back to his parent. I just want it to keep the ParentEntity id but nothing more. Up until now, no problem, I just delete the [NOTWANTED] line, and everything works as expected.

我的问题是:如何在特定情况下禁用级联删除?

My problem here is: how to disable the cascade delete in that specific case?

如果我仍然有父导航属性，那就很简单了:

If I still had the parent navigation property it would be as easy as:

modelBuilder.Entity<ChildEntity>()
    .HasRequired(c => c.parent)
    .WithMany(p => p.Childrens)
    .WillCascadeOndelete(false)

但是，如果没有导航属性，我不知道如何在删除时禁用级联(当然，不全局禁用它，也不针对每个表禁用它，而只是针对关系).

However without the navigation property I have no idea how I can achieve to disable the cascade on delete (without disabling it globally of course, nor per table, but just for the relation).

我现在所做的是将外键设置为可为空的 int，以便在删除时禁用级联，但这并不漂亮:

What I have done right now is to set the foreign key as a nullable int, in order to disable the cascade on delete, but that's not pretty:

public int? ParentEntityId; // Foreign Key - nullable just to disable cascade on delete

我怎样才能让它与流畅的 API 一起工作?觉得应该可以.

How can I get it to work with fluent API? Think it should be possible.

推荐答案

必须从关联的另一端配置:

You must configure it from the other side of the association:

modelBuilder.Entity<ParentEntity>()
    .HasMany(p => p.Children)
    .WithRequired()
    .HasForeignKey(c => c.ParentEntityId)
    .WillCascadeOnDelete(false);

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