private void TabPanel_DragDrop(object sender, DragEventArgs e)
{
//fixme:カッコカリ 範囲外にドロップすると端に行く
Point mp = TabPanel.PointToClient(new Point(e.X, e.Y));
var item = TabPanel.GetChildAtPoint(mp);
int index = TabPanel.Controls.GetChildIndex(item, false);
TabPanel.Controls.SetChildIndex((System.Windows.Forms.Control)e.Data.GetData(typeof(ImageLabel)), index);
TabPanel.Invalidate();
}