C# 通过一对多删除孤立项

我有以下代码：

public class Parent
{
  public int ParentId {get;set;}
  public ICollection<Child> Children {get;set;}
}

public class Child
{          
  public int ChildId {get;set;}
  public Parent Parent {get;set;}
}

公共类父类
{
public int ParentId{get；set；}
公共ICollection子项{get；set；}
}
公营儿童
{          
public int ChildId{get；set；}
公共父级{get；set；}
}

EF将其映射为一对多，无需任何额外努力。当我用新集合（另外3个项目）替换子集合时，子表中的旧孤立实体如下所示：

Id | Parent_Id
1     NULL       <-- orphan
2     NULL       <-- orphan
3     NULL       <-- orphan
4       1        <-- new
5       1        <-- new
6       1        <-- new

Id |父| Id
1 NULL据我所知，要识别关系，您需要包含作为子项主键一部分的父项主键。EF将允许您从集合中删除子项并为您删除它

仅仅拥有导航属性是行不通的。标识关系是数据库级别的概念，因此需要公开的主键id

在我的应用程序中，我有一个类似的模型。然而，我没有把孤儿带走，也没有培养他们。如果要删除某些子对象，请按以下方式执行：

//This line attaches a parent object to the session. EF will start monitoring it. 
Entry(parent).State = EntityState.Modified;

//This code is responsible for finding children to delete.
foreach (var child in parent.Children.Where(ch => ch.Deleted))
    //This line says EF that given child should be removed.
    //This line also causes that an object will be removed from Children collection.
    Entry(child).State = EntityState.Deleted;

SaveChanges();

Deleted是一个属性，如果要删除对象，我会将其设置为true

modelBuilder.Entity<Child>().HasKey(x => new { x.ChildId, x.Parent });

//This line attaches a parent object to the session. EF will start monitoring it. 
Entry(parent).State = EntityState.Modified;

//This code is responsible for finding children to delete.
foreach (var child in parent.Children.Where(ch => ch.Deleted))
    //This line says EF that given child should be removed.
    //This line also causes that an object will be removed from Children collection.
    Entry(child).State = EntityState.Deleted;

SaveChanges();