private void groupBox1_Paint(object sender, PaintEventArgs e)
{
     //背景颜色
     e.Graphics.Clear(System.Drawing.SystemColors.Control);
            
     SizeF fontSize = e.Graphics.MeasureString(groupBox1.Text, groupBox1.Font);
     //背景颜色
     e.Graphics.DrawString(groupBox1.Text, groupBox1.Font, Brushes.Black, (groupBox1.Width - fontSize.Width) / 2, 1);
     e.Graphics.DrawLine(Pens.CornflowerBlue, 1, 7, (groupBox1.Width - fontSize.Width) / 2, 7);
     e.Graphics.DrawLine(Pens.CornflowerBlue, (groupBox1.Width + fontSize.Width) / 2 - 4, 7, groupBox1.Width - 2, 7);

     e.Graphics.DrawLine(Pens.CornflowerBlue, 1, 7, 1, groupBox1.Height - 2);
     e.Graphics.DrawLine(Pens.CornflowerBlue, 1, groupBox1.Height - 2, groupBox1.Width - 2, groupBox1.Height - 2);
     e.Graphics.DrawLine(Pens.CornflowerBlue, groupBox1.Width - 2, 7, groupBox1.Width - 2, groupBox1.Height - 2);
}