void _listView_ItemMouseMove(object sender, ListViewItemMouseEventArgs e)
{
if (e.OriginalEventArgs.Button == MouseButtons.Left)
{
if (_dragItem != null)
{
_listView.DoDragDrop(new DataObject(LayoutHost.cstDragDropDataFormat, _dragItem.Tag as Type), DragDropEffects.Copy);
}
}
_dragItem = null;
}