Code

private void diagram_DrawCell(object sender, DrawCellEventArgs e)
{
	IGraphics g = e.Graphics;
	TableNode.Cell cell = e.Cell;
	RectangleF r = e.Bounds;
	PointF pivot = new PointF(r.X + r.Width / 2, r.Y + r.Height / 2);

	// draw rotated text
	Matrix savedTransform = g.Transform;

	g.TranslateTransform(pivot.X, pivot.Y);
	g.RotateTransform(20);
	g.TranslateTransform(-pivot.X, -pivot.Y);

	StringFormat format = new StringFormat();
	format.Alignment = StringAlignment.Center;
	format.LineAlignment = StringAlignment.Center;

	g.DrawString(cell.Text,
		cell.Font ?? e.Table.Font, Brushes.Black, r, format);

	g.Transform = savedTransform;
}