如何禁用链接表级联删除 EF 代码优先？

我想禁用级联删除链接表与实体框架代码第一。例如，如果许多用户有许多角色，并且我尝试删除一个角色，我希望该删除被阻止 除非目前没有任何用户与该角色相关联。我已经删除了 OnModelCreating中的级联删除约定:

protected override void OnModelCreating(DbModelBuilder modelBuilder) {
...
modelBuilder.Conventions.Remove<OneToManyCascadeDeleteConvention>();

然后我设置了用户角色链接表:

modelBuilder.Entity<User>()
.HasMany(usr => usr.Roles)
.WithMany(role => role.Users)
.Map(m => {
m.ToTable("UsersRoles");
m.MapLeftKey("UserId");
m.MapRightKey("RoleId");
});

然而当 EF 创建数据库时，它为外键关系创建了一个删除级联，例如。

ALTER TABLE [dbo].[UsersRoles]  WITH CHECK ADD  CONSTRAINT [FK_dbo.UsersRoles_dbo.User_UserId] FOREIGN KEY([UserId])
REFERENCES [dbo].[User] ([UserId])
ON DELETE CASCADE
GO


ALTER TABLE [dbo].[UsersRoles]  WITH CHECK ADD  CONSTRAINT [FK_dbo.UsersRoles_dbo.Role_RoleId] FOREIGN KEY([RoleId])
REFERENCES [dbo].[Role] ([RoleId])
ON DELETE CASCADE
GO

如何停止 EF 生成这个删除级联？

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最佳答案

I got the answer. :-) Those cascade deletes were being created because of ManyToManyCascadeDeleteConvention. You need to remove this convention to prevent it from creating cascade deletes for link tables:

modelBuilder.Conventions.Remove<ManyToManyCascadeDeleteConvention>();
小开

I believe that turning off ManyToManyCascadeDeleteConvention globally is not a wise option. Instead, it's better to turn it off only for the concerned table.

This can be achieved through editing the generated migration file, for property cascadeDelete. For example:

AddForeignKey("dbo.UsersRoles", "UserId", "dbo.User", "UserId", cascadeDelete: false);

小开

I agree with Ebram Khalil that turning it off for a single table is a good option. I like to stick as close to the automatically built migrations as I can, however, so I would set it up in OnModelCreating:

modelBuilder.Entity<User>()
.HasMany(usr => usr.Roles)
.WithMany(role => role.Users)
.Map(m => {
m.ToTable("UsersRoles");
m.MapLeftKey("UserId");
m.MapRightKey("RoleId");
})
.WillCascadeOnDelete(false);

I believe this preserves the delete going the other direction, so if both needed to be blocked (makes sense in this example) a similar call would need to be made starting with Entity<User>(Role)

Of course, this comes ages after the question was asked. So it may not have been valid in 2012.

小开

This works for me in EFCore 6.0.1 and MySql, according to ms docs.

Note: Don't forget to regenerate your migration files after this.

// In your dbContext class
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder
.Entity<User>()
.HasMany(usr => usr.Roles)
.WithMany(role => role.Users)
.OnDelete(DeleteBehavior.Restrict);
}

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