实体框架核心级联删除一对多关系

Question

public class Station : IEntitie
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public virtual ICollection<RegulatorySchedule> RegulatoryScheduleDispatchStations { get; set; }    

    public virtual ICollection<RegulatorySchedule> RegulatoryScheduleDestinationStations { get; set; }   
}

public class RegulatorySchedule : IEntitie
{
    [Key]
    public int Id { get; set; }

    public virtual Station DispatchStation { get; set; }      

    public virtual Station DestinationStation { get; set; }     
}


protected override void OnModelCreating(ModelBuilder modelBuilder)
{
        modelBuilder.Entity<RegulatorySchedule>()
            .HasOne(s => s.DestinationStation)
            .WithMany(s => s.RegulatoryScheduleDestinationStations)
            .OnDelete(Microsoft.EntityFrameworkCore.Metadata.DeleteBehavior.Restrict);

        modelBuilder.Entity<RegulatorySchedule>()
            .HasOne(s => s.DispatchStation)
            .WithMany(s => s.RegulatoryScheduleDispatchStations)
            .OnDelete(Microsoft.EntityFrameworkCore.Metadata.DeleteBehavior.Restrict);
}

仅当我在删除时清楚地暴露行为时,才会在迁移期间创建数据库Restrict OnDelete (Microsoft.EntityFrameworkCore.Metadata.DeleteBehavior.Restrict).否则,它会抛出异常:

"在表'RegulatorySchedules'上引入FOREIGN KEY约束'FK_RegulatorySchedules_Stations_DispatchStationId'可能会导致循环或多个级联路径.指定ON DELETE NO ACTION或ON UPDATE NO ACTION,或修改其他FOREIGN KEY约束."

我需要删除表格的站点站点以及与表格相关的属性RegulatorySchedules DispatchStation和DestinationStation暴露于NULL.但是Restrict选项当你删除我无法放入的SetNull时会有异常.告诉我怎么样？

Answer 1

描述的"问题"与实体框架无关 - 这是对MS SQL Server本身的限制.具有多个FK的表可能只有一个具有级联删除.

因此,只要您需要两个FK进行级联 - 您应该在代码中实现这样的"清理".将一个(或两个)FK设置为DeleteBehavior.Restrict,并在控制器/服务中删除之前Station手动查找并删除所有相关的RegulatorySchedule

Answer 2

德米特里的回答完美无缺。对于任何未来的旅行者，下面的映射表的工作样本。

代码位于类中的OnModelCreating(ModelBuilder modelBuilder)方法中 DbContext：

modelBuilder.Entity<AB>()
            .HasKey(e => new { e.AId, e.BId});

modelBuilder.Entity<AB>()
            .HasOne(e => e.A)
            .WithMany(e => e.ABs)
            .HasForeignKey(e => e.AId)
            .OnDelete(DeleteBehavior.Cascade); // <= This entity has cascading behaviour on deletion

modelBuilder.Entity<AB>()
            .HasOne(e => e.B)
            .WithMany(e => e.ABs)
            .HasForeignKey(e => e.BId)
            .OnDelete(DeleteBehavior.Restrict); // <= This entity has restricted behaviour on deletion