Windows Phone 上拉刷新、下拉刷新

ScrollViewer scrollViewer = new ScrollViewer();
// 构造函数
public MainPage()
{
    InitializeComponent();
    for (int x = ; x <= ; x++)
    {
        listBox1.Items.Add(x);
    }
}

private double actuableOffset, validStartOffset;
private bool mplStarted;
protected override void OnManipulationStarted(ManipulationStartedEventArgs e)
{
     base.OnManipulationStarted(e);
     mplStarted = true;
}

protected override void OnManipulationCompleted(ManipulationCompletedEventArgs e)
{
     //150是下拉的距离可以自己调适
   if (actuableOffset >  && scrollViewer.VerticalOffset == )
    {
        MessageBox.Show("Head pull bingo!");
    }
    if (actuableOffset < - && scrollViewer.VerticalOffset == scrollViewer.ScrollableHeight)
    {
        MessageBox.Show("Tail pull bingo!");
    }
        base.OnManipulationCompleted(e);
}

protected override void OnMouseMove(MouseEventArgs e)
{
    //head capture startRelative
    if (scrollViewer.VerticalOffset == )
    {
        if (mplStarted)
        {
            mplStarted = false;
            validStartOffset = e.GetPosition(null).Y;
         }
         actuableOffset = e.GetPosition(null).Y - validStartOffset;
     }
      //tail
      if (scrollViewer.VerticalOffset == scrollViewer.ScrollableHeight)
      {
          if (mplStarted)
          {
              mplStarted = false;
              validStartOffset = e.GetPosition(null).Y;
          }
          actuableOffset = e.GetPosition(null).Y - validStartOffset;
        }
        //UIControlHelper.FindFirst<Pivot>().Title = actuableOffset;
        base.OnMouseMove(e);
}