public static IEnumerable <XObject> DescendantObjects(this XObject source)
{
source.NotNull(nameof(source));
return(Enumerable
.Empty <XObject>()
.Concat(
(source as XElement)?.Attributes() // T is covariant in IEnumerable<T>.
?? Enumerable.Empty <XObject>())
.Concat(
(source as XContainer)?
.DescendantNodes()
.SelectMany(descendant => Enumerable
.Repeat <XObject>(descendant, 1)
.Concat(
(descendant as XElement)?.Attributes() // T is covariant in IEnumerable<T>.
?? Enumerable.Empty <XObject>()))
?? Enumerable.Empty <XObject>()));
}
