EF Inserting Duplicate Parent Objects

Question

I have two classes:

public class Foo
{
    public int FooId {get;set;}
    public virtual ICollection Bars {get;set;}
}

public class Bar
{
    pu         


        

Answer 1

Try

var bar = new Bar();
context.Bars.Add(bar);
bar.Foo == foo;
context.SaveChanges();

It seems like the entity key isn't being set uniquely when assignment occurs before the entity is added to the context.

Answer 2

Loading the foo with the same context as adding the new bar with the related foo won't cause a duplication. My guess is that your real code uses two different contexts.

The only thing to change in the code (which won't compile because foo is an IQueryable<Foo> and not a Foo) is to materialize the foo, for example:

var foo = (from f in context.Foos
          where f.FooId == 1
          select f).Single();

Other than that the code snippet is fine.

Answer 3

Not sure if this is the best practice, but when I ran into this issue I ended up setting the parent entity to Null but maintain any FK reference, this stopped the parent entity from being inserted on child entities:

var bar = new Bar();
context.Bars.Add(bar);
bar.Foo == null;
bar.FooId = existingFooParent.Id;
context.SaveChanges();

Answer 4

I think that you are approaching the problem in the wrong way. You want to add the new Bar object to your existing foo object instead of the other way round:

var foo = from f in context.Foos
          where f.FooId == 1
          select f;

var bar = new Bar();
foo.Bars.Add(bar);

context.SaveChanges();