C#在拖放时实现ListView中的自动滚动

private void listView1_DragEnter(object sender, DragEventArgs e)
{
    if (e.Data.GetDataPresent(DataFormats.Text))
    {
        e.Effect = DragDropEffects.Move;
    }
    else
    {
        e.Effect = DragDropEffects.None;
    }
}

private void listView1_DragOver(object sender, DragEventArgs e)
{
    Point clientPoint = listView1.PointToClient(new Point(e.X, e.Y));
    ListViewItem item = listView1.GetItemAt(clientPoint.X, clientPoint.Y);

    if (item != null)
    {
        if (clientPoint.Y< item.Bounds.Top + item.Bounds.Height / 4)
        {
            listView1.EnsureVisible(item.Index - 1);
        }
        else if (clientPoint.Y > item.Bounds.Bottom - item.Bounds.Height / 4)
        {
            listView1.EnsureVisible(item.Index + 1);
        }
    }
}

private void listView1_DragDrop(object sender, DragEventArgs e)
{
    string data = (string)e.Data.GetData(DataFormats.Text);
    ListViewItem item = new ListViewItem(data);
    listView1.Items.Add(item);
}