Transparent background on picturebox

public class Test_PictureBox : System.Windows.Forms.PictureBox
{

    public Test_PictureBox()
    {
        this.Width = 100;
        this.Height = 100;

        SetTransparenz();
    }

    private void SetTransparenz()
    {
        this.SetStyle(System.Windows.Forms.ControlStyles.Opaque, true);
        this.SetStyle(System.Windows.Forms.ControlStyles.OptimizedDoubleBuffer, false);
        this.SetStyle(System.Windows.Forms.ControlStyles.ResizeRedraw, true);
    }

    protected override System.Windows.Forms.CreateParams CreateParams
    {
        get
        {
            System.Windows.Forms.CreateParams cp = base.CreateParams;
            cp.ExStyle = cp.ExStyle | 0x20;
            // Turn on WS_EX_TRANSPARENT
            return cp;
        }
    }

}

class OvalPictureBox : PictureBox
{
    public OvalPictureBox()
    {
        this.BackColor = Color.Transparent;
    }
    protected override void OnResize(EventArgs e)
    {
        base.OnResize(e);
        using (var gp = new GraphicsPath())
        {
            gp.AddEllipse(new Rectangle(0, 0, this.Width - 1, this.Height - 1));
            this.Region = new Region(gp);
        }
    }
}