获取当前Panel的PARENT的表单大小

Question

运行此代码，在对话框打开时通过我的应用程序创建BMP，以减少用户对无法访问的内容的混淆（直到对话框关闭）。

Bitmap bmp = new Bitmap(DisplayRectangle.Width, DisplayRectangle.Height);
            using (Graphics G = Graphics.FromImage(bmp))
            {
                G.CompositingMode = System.Drawing.Drawing2D.CompositingMode.SourceOver;
                G.CopyFromScreen(this.PointToScreen(new Point(0, 0)), new Point(0, 0), this.DisplayRectangle.Size);
                double percent = 0.60;
                Color darken = Color.FromArgb((int)(255 * percent), Color.Black);
                using (Brush brsh = new SolidBrush(darken))
                {
                    G.FillRectangle(brsh, this.DisplayRectangle);
                }
            }

            // put the darkened screenshot into a Panel and bring it to the front:
            using (Panel p = new Panel())
            {
                p.Location = new Point(0, 0);
                p.Size = this.ClientRectangle.Size;
                p.BackgroundImage = bmp;
                this.Controls.Add(p);
                p.BringToFront();

                // display your dialog somehow:
                frmcollecting frmcollecting = new frmcollecting(pxid);
                frmcollecting.ShowDialog();

问题在于它创建了面板上的bmp（pnlActive），但我希望它在整个应用程序上。 如何获得尺寸并将DisplayRectangle更改为“frmMainPage”？

Ty求助