MARKUS

        public static IEnumerable<DependencyObject> FindAllChildren(this DependencyObject dpo, Predicate<DependencyObject> predicate)

        {

            //var results = new List<DependencyObject>();

            //if (predicate == null)

            //    yield return results;

            for (int i = 0; i < VisualTreeHelper.GetChildrenCount(dpo); i++)

            {

                var child = VisualTreeHelper.GetChild(dpo, i);

                if (predicate(child))

                    yield return child;// results.Add(child);

                var subChildren = child.FindAllChildren(predicate);

                foreach (var item in subChildren)

                {

                    yield return item;

                }

                //results.AddRange(subChildren);

            }

        }