Code

void OnDrawForeground(object sender, DiagramEventArgs e)
{
	var rulerBounds = diagram.Bounds;
	rulerBounds.Y = diagView.ScrollY;
	rulerBounds.Height = 6;

	e.Graphics.FillRectangle(
		MindFusion.Drawing.Brushes.White, rulerBounds);

	int startX = (int)(e.VisibleRect.X / 10) * 10;
	for (int x = startX; x < e.VisibleRect.Right; x += 10)
	{
		e.Graphics.DrawString(
			x.ToString(), diagram.Font,
			MindFusion.Drawing.Brushes.Black,
			x, rulerBounds.Y + 1);
	}
}