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 > 150 && scrollViewer.VerticalOffset == 0)
            {
                MessageBox.Show("Head pull bingo!");
            }
            if(actuableOffset<-150&&scrollViewer.VerticalOffset==scrollViewer.ScrollableHeight)
            {
                MessageBox.Show("Tail pull bingo!");
            }
            base.OnManipulationCompleted(e);
        }
protected override void OnMouseMove(MouseEventArgs e)
        {
            //head capture startRelative
            if ( scrollViewer.VerticalOffset == 0)
            {
                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);
        }