EF Core 8多父级模型级联删除与SuperChild批量查询方案咨询

使用.NET Core 8和EF Core 8开发（AutoMapper与当前问题无关），现有实体类如下：

public class MainA {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }

    public virtual ICollection<ChildA> ChildsA { get; set; }
    public virtual ICollection<ChildB> ChildsB { get; set; }
    public virtual ICollection<ChildC> ChildsC { get; set; }
}

public class ChildA {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }

    public virtual ICollection<SubChildA> Childs1 { get; set; }
}

public class SubChildA {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }

    public virtual ICollection<SuperChild> Childs1 { get; set; }
}

public class ChildB {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }

    public virtual ICollection<SuperChild> Childs1 { get; set; }
}

public class ChildC {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }

    public virtual ICollection<SuperChild> Childs1 { get; set; }
}

public class SuperChild {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }
}

遇到的问题 #

• 使用Owns...配置可实现级联删除，但无法直接查询所有SuperChild数据，必须关联其他表才能查询
• 采用常规关系配置时，SuperChild会存在多个外键，且无法实现删除MainA时级联删除所有关联SuperChild的需求
• 尝试过创建中间链接模型（示例如下），但删除MainA时仅会删除链接表数据，SuperChild数据仍会残留：

public class ChildB {
    public string Prop1 { get; set; }
    public string Prop2 { get; set; }

    public virtual ICollection<ChildB_Link_SuperChild> Childs1 { get; set; }
}

public class ChildB_Link_SuperChild
{
    public Guid ChildBId { get; set; }
    public virtual ChildB ChildB { get; set; }

    public Guid SuperChildId { get; set; }
    public virtual SuperChild SuperChild { get; set; }
}

public class ChildB_Link_SuperChildConfiguration : IEntityTypeConfiguration<ChildB_Link_SuperChild>
{
    public void Configure(EntityTypeBuilder<ChildB_Link_SuperChild> builder)
    {
        builder.HasKey(rd => new { rd.ChildBId, rd.SuperChildId });

        builder.HasOne(x => x.ChildB )
            .WithMany(x => x.Childs1)
            .HasForeignKey(x => x.ChildBId)
            .OnDelete(DeleteBehavior.Cascade);
    
        builder.HasOne(x => x.SuperChild)
            .WithOne()
            .HasForeignKey<ChildB_Link_SuperChild>(x => x.SuperChildId)
            .OnDelete(DeleteBehavior.Cascade);
    }
}

当前考虑的方案 #

计划采用Owns配置结合Concat查询的方式，示例代码如下：

db.Set<MainA>()
    .SelectMany(x =>
        x.ChildsA.SelectMany(y => y.Childs1).SelectMany(z => z.Childs1)
            .Concat(x.ChildsB.SelectMany(y => y.Childs1))
            .Concat(x.ChildsC.SelectMany(y => y.Childs1))
    )
    .ToList();

疑问 #

1. 该方案是否为最优解？
2. 有无其他实现思路？
3. 该Concat语句能否被EF Core正确翻译且性能良好？

内容的提问来源于stack exchange，提问作者Flo