private void AddExample(PaintEventArgs e)
{
    PointF point1 = new PointF(120.5F, 120F);
    SizeF size1 = new SizeF(20.5F, 20.5F);
    RectangleF rect1 = new RectangleF(point1, size1);
    PointF point2 = new PointF(rect1.Right, rect1.Bottom);
    if (point2 != PointF.Add(point1, size1))
        e.Graphics.DrawString("They are not equal", this.Font, Brushes.Red, rect1);
    else
        e.Graphics.DrawString("They are equal", this.Font, Brushes.Black, rect1);
}