private void ArrangeTree()
{
using (Graphics gr = picTree.CreateGraphics())
{
// Arrange the tree once to see how big it is.
float xmin = 0, ymin = 0;
root.Arrange(gr, ref xmin, ref ymin);
// Arrange the tree again to center it horizontally.
xmin = (this.ClientSize.Width - xmin) / 2;
ymin = 10;
root.Arrange(gr, ref xmin, ref ymin);
}
picTree.Refresh();
}