DepenencyProperty AddOwner是否包括FrameworkPropertyMetadata？

Question

When a DependencyProperty that has FrameworkPropertyMetadataOptions.BindsTwoWayByDefault set is reused in a different control via AddOwner(typeof(NewOwner)) does this reuse include the two way binding behavior or should I set it like AddOwner(typeof(NewOwner, new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault)) .

I would expect it does but somehow it looks like it doesn't. When you check the metadata using GetMetadata on the property I can't check it for the added owner.

See this example:

public class MyControl : Control
{
    public object SelectedItem
    {
        get { return (object)GetValue(SelectedItemProperty); }
        set { SetValue(SelectedItemProperty, value); }
    }

    public static readonly DependencyProperty SelectedItemProperty = ListBox.SelectedItemProperty.AddOwner(typeof(MyControl));
}

then inspect using:

  var x = ListBox.SelectedItemProperty.GetMetadata(typeof(ListBox)) as FrameworkPropertyMetadata;
  bool bx = x.BindsTwoWayByDefault;  // true;
  var y = MyControl.SelectedItemProperty.GetMetadata(typeof(MyControl)) as FrameworkPropertyMetadata;
  bool by = y.BindsTwoWayByDefault; // null pointer excpetion

Answer 1

Per documentation :

Adds another type as an owner of a dependency property that has already been registered, providing dependency property metadata for the dependency property as it will exist on the provided owner type .