private void tvFiles_DragOver(object sender, DragEventArgs e)
{
// Retrieve the client coordinates of the mouse position.
Point targetPoint = tvFiles.PointToClient(new Point(e.X, e.Y));
// Select the node at the mouse position.
tvFiles.SelectedNode = tvFiles.GetNodeAt(targetPoint);
if (LastNode != null)
{
LastNode.Collapse();
}
CurrentNode.Expand();
}