semi transparent panel in c# .net on Windows 8.1

public class MyPanel : System.Windows.Forms.Panel
{
    public MyPanel() : base()
    {
        this.SetStyle(ControlStyles.UserPaint, true);
        this.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
        this.SetStyle(ControlStyles.ResizeRedraw, true);
        this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
        this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
    }

    protected override CreateParams CreateParams
    {
        get
        {
            var cp = base.CreateParams;
            cp.ExStyle |= 0x00000020;
            return cp;
        }
    }

    protected override void OnPaintBackground(PaintEventArgs e)
    {
        // Do not paint background.
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        e.Graphics.Clear(System.Drawing.Color.White);
        e.Graphics.CopyFromScreen(this.PointToScreen(new Point(0, 0)), new Point(0, 0), new Size(this.Width, this.Height));
        e.Graphics.FillRectangle(new SolidBrush(System.Drawing.Color.FromArgb(120, System.Drawing.Color.Gray)), new Rectangle(new Point(0, 0), this.Size));
    }
}