从父实体中删除子实体-EF Core 2.2

Question

I would like to remove an item from collection which exist in one entity. The problem I face is:

-entity is being removed from context

-after save changes the entity still exists

The Parent object:

public class MyObject
{
    public int Id { get; private set; }
    public ICollection<ChildObject> ChildObjcets { get; private set; }

    public void RemoveChildObject(ChildObject @object)
    {
        this.ChildObjcets.Remove(@object);
    }
}

the Child object:

 public class ChildObject
 {
    public int Id { get; private set; }

    public MyObject MyObject { get; set; }
    public int MyObjectId { get; set; }
}

What I have tried:

public void Proceed()
{
     //myObject contain 4 child objects inside
     var myObject = _repo.GetMyObject();
     var childObject = _repo.GetChildObject();

     myObject.RemoveChildObject(childObject);
    //myObject contain 3 items now

}

Before saving the changes I do not see removed entity in the change tracker - the state should be Removed?

var childObjects = ChangeTracker.Entries().Where(x => x.Entity is ChildObject).ToList(); // returns 3 - the removed one does not exist

However when I save changes then the root object still contain 4 entities - so the child object was not removed at all

_repo.SaveChanges();       
var myObject = _repo.GetMyObject();

Any idea how to handle removing child object from root entity?

Answer 1

在Entity Framework 6中，执行此操作的更快方法是

context.Children.RemoveRange(parent.Children)

Answer 2

Removing the ChildObject from ChildObjcets (also, note the typo) collection means removing the relation rather than removing the entity from DbContext . To completely remove the entity you need to explicitly call Remove on the DbSet<ChildObject> which you cannot do directly from your root object.

I suggest moving this operation to your _repo whatever it actually references to. It should have access to DbContext hence any DbSet<> .