拖放麻烦

Question

网格视图移动，但是当我想拖动到任何位置时，它会返回到开始位置。我究竟做错了什么？我想我差不多完成了拖拉。

代码：

private void gridSlider_ManipulationCompleted(object sender, ManipulationCompletedRoutedEventArgs e)
{
    var _GridView = sender as Windows.UI.Xaml.Controls.GridView;
    _GridView.RenderTransform = null;

    var _Column = System.Convert.ToInt32(_GridView.GetValue(Grid.ColumnProperty));
    if (_Column <= 0 && e.Cumulative.Translation.X > _GridView.RenderSize.Width * .5)
    {
        _GridView.SetValue(Grid.ColumnProperty, 1);
    }
    else if (_Column == 1 && e.Cumulative.Translation.X < _GridView.RenderSize.Width * -.5)
    {
        _GridView.SetValue(Grid.ColumnProperty, 0);
    }

    var _Row = System.Convert.ToInt32(_GridView.GetValue(Grid.RowProperty));
    if (_Row <= 0 && e.Cumulative.Translation.Y > _GridView.RenderSize.Height * .5)
        _GridView.SetValue(Grid.RowProperty, 1);
    else if (_Row == 1 && e.Cumulative.Translation.Y < _GridView.RenderSize.Height * -.5)
        _GridView.SetValue(Grid.RowProperty, 0);
}

private void gridSlider_ManipulationDelta(object sender, ManipulationDeltaRoutedEventArgs e)
{
    var _GridView = sender as Windows.UI.Xaml.Controls.GridView;
    var _Transform = (_GridView.RenderTransform = (_GridView.RenderTransform as TranslateTransform) ?? new TranslateTransform()) as TranslateTransform;
    _Transform.X += e.Delta.Translation.X;
    _Transform.Y += e.Delta.Translation.Y;
}

Xaml代码：

 <StackPanel Name="TransportControlsPanel" HorizontalAlignment="Center" Grid.Row="1" Margin="351,0,0,0" >
      <GridView x:Name="gridSlider" Width="604" AllowDrop="True" HorizontalAlignment="Center" Height="92" VerticalAlignment="Center" Visibility="Collapsed" SelectionMode="None" ManipulationCompleted="gridSlider_ManipulationCompleted" ManipulationDelta="gridSlider_ManipulationDelta">

           <Slider x:Name="timelineSlider" AllowDrop="True" Margin="200,0,10,49" Width="192" Height="25" VerticalAlignment="Bottom" HorizontalAlignment="Center" Visibility="Collapsed" Background="Gray"/>

      </GridView>
 </StackPanel>