private void MainForm_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
{
    Font font = new Font("Tahoma", 11, GraphicsUnit.Pixel);
    SizeF size = e.Graphics.MeasureString(drawText, font);
    this.Text = size.Width.ToString();
    e.Graphics.DrawRectangle(new Pen(Color.Red, 1), 0.0F, 0.0F, size.Width, size.Height);
    e.Graphics.DrawString(drawText, font, Brushes.Black, new PointF(0, 0));
}