ListBox 是否滚动到底部

public class MyListBox: ListBox
    {
        public MyListBox() : base()
        {
            AddHandler(ScrollViewer.ScrollChangedEvent, new ScrollChangedEventHandler(ScrollView_ScrollChanged), true);
        }

        #region 是否滚动到底部

        private void ScrollView_ScrollChanged(object sender, ScrollChangedEventArgs e)
        {
            if (e.OriginalSource is ScrollViewer scrollViewer)
            {
                var isBottom = ListBoxHelper.IsVerticalScrollBarAtButtom(scrollViewer);
                SetIsScrolledBottom(this, isBottom);
            }
        }
        
        /// <summary>
        /// 判断ScrollViewer是否滚动到底部
        /// </summary>
        /// <param name="scrollViewer"></param>
        /// <returns></returns>

        public static bool IsScrolledToButtom(ScrollViewer scrollViewer)
        {
            var isBottom = false;
            if (Math.Abs(scrollViewer.VerticalOffset) > 0)
            {
                if (scrollViewer.VerticalOffset + scrollViewer.ViewportHeight == scrollViewer.ExtentHeight)
                {
                    isBottom = true;
                }
            }

            if (scrollViewer.VerticalScrollBarVisibility == ScrollBarVisibility.Disabled
                || scrollViewer.VerticalScrollBarVisibility == ScrollBarVisibility.Hidden
                || scrollViewer.ScrollableHeight <= 0)
            {
                isBottom = true;
            }
            return isBottom;
        }

        public static readonly DependencyProperty IsScrolledBottomProperty = DependencyProperty.Register(
            "IsScrolledBottom", typeof(bool), typeof(MyListBox), new PropertyMetadata(default(bool)));

        public static void SetIsScrolledBottom(DependencyObject element, bool value)
        {
            element.SetValue(IsScrolledBottomProperty, value);
        }

        public static bool GetIsScrolledBottom(DependencyObject element)
        {
            return (bool)element.GetValue(IsScrolledBottomProperty);
        }

        #endregion

    }

属性IsScrolledBottom，表示当前已经滚动到底部

PS:上面写法还是有点小问题。
当前列表没有触发滚动到底部后，往列表中添加数据，添加过程中并不会触发ScrollChanged。
然后属性IsScrolledBottom就不准确了。
解决：对ListBox.Items.CollectionChanged添加监听，在触发事件中，调用IsScrolledToButtom方法，主动获取并设置当前IsScrolledBottom属性