一对多级联删除

Question

删除父记录时，我希望 EF 删除子记录，而不必执行以下操作：

public Foo
{
    [Key]
    public int FooID { get; set; }
    public string Foo_Name { get; set; }
    //One to many with bar
    public virtual  List<Bar> Bar_List { get; set; }
}

public Bar
{
    [Key]
    public int BarID { get; set; }
    public string Bar_Name { get; set; }
    //One to Many with baz
    public virtual List<Baz> Baz_List { get; set; }
}

public Baz
{
    [Key]
    public int BazID { get; set; }
    public string Baz_Name { get; set; }
}

这就是我要删除子记录的操作

using(var context = new FooBarBazContext())
{
    var Foo_List = context.Foos.Where(w => w.Foo_Name == "FooName1234").ToList();

    foreach(var foo in Foo_List)
    {
         foreach(var bar in foo.Bar_List)
         {
              bar.Baz_List.ToList().ForEach(i => context.Bazs.Remove(i));
         }
         foo.Bar_List.ToList().ForEach(i => context.Bars.Remove(i));
         context.Foos.Remove(foo);
         context.Entry<Foo>(foo).State = EntityState.Deleted;
         context.SaveChanges();
    }
}

编辑 - 解决方案

好的，我需要为每个子对象添加一个父导航属性

public Foo
{
    [Key]
    public int FooID { get; set; }
    public string Foo_Name { get; set; }
    //One to many with bar
    public virtual  List<Bar> Bar_List { get; set; }
}

public Bar
{
    [Key]
    public int BarID { get; set; }
    public string Bar_Name { get; set; }
    //One to Many with baz
    public virtual List<Baz> Baz_List { get; set; }
    public virtual Foo FooObject [ get; set; } //<-- Navigation property for Foo
}

public Baz
{
    [Key]
    public int BazID { get; set; }
    public string Baz_Name { get; set; }
    public virtual Bar BarObject { get; set; } //<-- Navigation property for Bar
}

然后我需要将以下内容添加到 OnModelCreating 事件中：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
     modelBuilder.Entity<Foo>().HasKey(x => x.FooID)
                               .HasMany(x => x.Bar_List)
                               .WithOptional(x => x.FooObject)
                               .WillCascadeOnDelete(true);

     modelBuilder.Entity<Bar>().HasKey(x => x.BarID)
                               .HasMany(x => x.Baz_List)
                               .WithOptional(x => x.BarObject)
                               .WillCascadeOnDelete(true);

     base.OnModelCreating(modelBuilder);
}

现在 EF 为我完成了所有繁重的工作：

var foosToRemove = context.Foos.Where(w => w.Foo_Name == "FooName1234").ToList();

foreach (var fooToRemove in foosToRemove)
{
      context.Entry<Foo>(fooToRemove).State = EntityState.Deleted;
}
int results = context.SaveChanges();

Answer 1

您需要在实体上设置级联删除。

见Entity Framework 4.3 delete cascade with code first (Poco)

{
//...
modelBuilder.Entity<Parent>()
    .HasMany(e => e.ParentDetails)
    .WithOptional(s => s.Parent)
    .WillCascadeOnDelete(true);
//...

需要注意的是，当您删除父实体时，上下文中的相关子实体也会发出删除语句。例如，有 1000 个孩子的父母将发出 1001 条语句（1 条删除用于父母，1000 条用于孩子）。这样做是为了使上下文中的实体保持最新。

为避免额外的子删除，请在 SaveChanges 之前分离子，并允许数据库中的外键执行删除。如果您先编写代码，则需要添加该外键关系。

请参阅How Cascade Delete Really Works in EF 了解更多信息。