using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Media;

namespace ListViewScroll
{
    public static class VisualTreeHelperExtensions
    {
        public static T GetFirstDescendantsOfType<T>(this DependencyObject obj) where T : DependencyObject
        {
            return obj.GetDescentantsOfType<T>().FirstOrDefault();
        }
        public static IEnumerable<T> GetDescentantsOfType<T>(this DependencyObject obj) where T : DependencyObject
        {
            return obj.GetDescendants().OfType<T>();
        }
        public static IEnumerable<DependencyObject> GetDescendants(this DependencyObject obj)
        {
            var queue = new Queue<DependencyObject>();
            var count = VisualTreeHelper.GetChildrenCount(obj);
            for(int i=0;i<count;++i)
            {
                var child = VisualTreeHelper.GetChild(obj, i);
                yield return child;
                queue.Enqueue(child);
            }
            while( queue.Any())
            {
                var parent = queue.Dequeue();
                var count2 = VisualTreeHelper.GetChildrenCount(parent);

                for(int i=0;i<count2;++i)
                {
                    var child = VisualTreeHelper.GetChild(parent, i);
                    yield return child;
                    queue.Enqueue(child);
                }
            }
        }

    }
}