//自定義依賴屬性用來監視ListBox滾動到底事件
    public class ListBoxScrollToBottomNotify
    {
        public static ICommand GetScrollToBottomCommand(DependencyObject obj)
        {
            return (ICommand)obj.GetValue(ScrollToBottomCommandProperty);
        }

        public static void SetScrollToBottomCommand(DependencyObject obj, ICommand value)
        {
            obj.SetValue(ScrollToBottomCommandProperty, value);
        }

        //滾動到底問時響應的事件
       public static readonly DependencyProperty ScrollToBottomCommandProperty =
            DependencyProperty.RegisterAttached("ScrollToBottomCommand", typeof(ICommand), typeof(ListBoxScrollToBottomNotify), new PropertyMetadata(null, OnCommandChanged));

        static void OnCommandChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ListBox lb = d as ListBox;
            if (lb != null)
            {
                //確定只繫結一次ListBox的Loaded事件
                if (e.OldValue == null)             
                {
                    lb.Loaded += new RoutedEventHandler(OnListBoxLoaded);
                }
            }
        }
        static void OnListBoxLoaded(object sender, RoutedEventArgs e)
        {
                ListBox lb = sender as ListBox;
                ScrollViewer scrollViewer = FindChildOfType<ScrollViewer>(lb);
                if (scrollViewer != null)
                {
                    VerticalOffsetOfScrollViewNotify monitorVO = new VerticalOffsetOfScrollViewNotify();
                    monitorVO.Attached(scrollViewer);
                    monitorVO.VerticalOffsetChanged = () =>
                    {
                        double verticalOffset = Math.Round(scrollViewer.VerticalOffset);
                        double scrollableHeight = Math.Round(scrollViewer.ScrollableHeight);
                        if (verticalOffset >= scrollableHeight)
                        {
                            ICommand command= GetScrollToBottomCommand(lb);
                            command.Execute(null);
                        }
                    };
                }
        }
        //獲取子型別
        static T FindChildOfType<T>(DependencyObject root) where T : class
        {
            var queue = new Queue<DependencyObject>();
            queue.Enqueue(root);

            while (queue.Count > 0)
            {
                DependencyObject current = queue.Dequeue();
                for (int i = VisualTreeHelper.GetChildrenCount(current) - 1; 0 <= i; i--)
                {
                    var child = VisualTreeHelper.GetChild(current, i);
                    var typedChild = child as T;
                    if (typedChild != null)
                    {
                        return typedChild;
                    }
                    queue.Enqueue(child);
                }
            }
            return null;
        }
    }
    //監測ListBox中ScrollView的VerticalOffset改變
    public class VerticalOffsetOfScrollViewNotify
    {
        //通過監控ListBox的MouseMove事件和ManipulationCompleted事件的效果並不好,
        //當手指在螢幕上划動後ListBox會因為慣性,再滾動一段距離.這樣使用前兩個事件就不能判斷滾動的最後位置
        //現在改成通過依賴屬性繫結到ListBox的ScrollView的VerticalOffset來實現
        DependencyProperty VerticalOffsetProperty;

        public VerticalOffsetOfScrollViewNotify()
        {
                 VerticalOffsetProperty = DependencyProperty.RegisterAttached("VerticalOffset", typeof(double), typeof(VerticalOffsetOfScrollViewNotify), new PropertyMetadata(OnVerticalOffsetChanged));
        }
        public  void OnVerticalOffsetChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (VerticalOffsetChanged != null)
            {
                 VerticalOffsetChanged();
            }
        }

        public Action VerticalOffsetChanged { get; set; }
        public void Attached(FrameworkElement ele)
        {
            if (ele != null)
            {
                ScrollViewer scrollViewer = ele as ScrollViewer;
                Binding binding = new Binding("VerticalOffset") { Source = scrollViewer };
                scrollViewer.SetBinding(VerticalOffsetProperty, binding);
            }
        }
    }