How to remove child one to many related records in EF code first database?

c# code-first entity-framework

Question

Well, I have one-to-many related model:

public class Parent
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Child> Children { get; set; }
}

public class Child
{
    public int Id { get; set; }
    public string ChildName { get; set; }
}

What I want to do is clear Parent.Children and remove related child entities from database. I've already tried:

Database context class:

modelBuilder.Entity<Parent>()
            .HasMany(p => p.Children)
            .WithOptional()
            .WillCascadeOnDelete(true);

this works fine, but I still have redundant records in database with Parent_Id = null fields when I do

parent.Children.Clear();
repository.InsertOrUpdate(parent);

in my repository class. Also the same behavior is when I do:

modelBuilder.Entity<Parent>()
            .HasMany(pr => pr.Children)
            .WithOptional(ri => ri.Parent)
            .WillCascadeOnDelete(true);

with additional Parent property in Child class

public class Child
{
    ...
    public Parent Parent { get; set; }
    ...
}

or when I do

modelBuilder.Entity<Child>()
            .HasOptional(p => p.Parent)
            .WithMany(p => p.Children)
            .HasForeignKey(p => p.Parent_Id)
            .WillCascadeOnDelete(true);

with additional Parent_Id property in Child class

public class Child
{
     ...
     public int Parent_Id { get; set; }
     ...
}

So, how can I configure cascade deleting correctly? Or how should I supposed to remove those child entities? I assume this is casual task but I'm just missing something.

1
65
11/9/2015 8:38:20 AM

Accepted Answer

Cascading delete has no effect here because you don't delete the parent but just call InsertOrUpdate. The correct procedure is to delete the children one-by-one, like so for example:

using (var context = new MyContext())
{
    var parent = context.Parents.Include(p => p.Children)
        .SingleOrDefault(p => p.Id == parentId);

    foreach (var child in parent.Children.ToList())
        context.Children.Remove(child);

    context.SaveChanges();
}
65
5/20/2013 6:28:45 PM

Popular Answer

In EF6 a faster way to do the operation is...

 context.Children.RemoveRange(parent.Children)


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