C# Panel控件截图

[System.Runtime.InteropServices.DllImportAttribute("gdi32.dll ")]
        private static extern bool BitBlt(
        IntPtr hdcDest, // handle to destination DC
        int nXDest, // x-coord of destination upper-left corner
        int nYDest, // y-coord of destination upper-left corner
        int nWidth, // width of destination rectangle
        int nHeight, // height of destination rectangle
        IntPtr hdcSrc, // handle to source DC
        int nXSrc, // x-coordinate of source upper-left corner
        int nYSrc, // y-coordinate of source upper-left corner
        System.Int32 dwRop // raster operation code
        );

Graphics g1 = panel1.CreateGraphics();
            Image myImage = new Bitmap(this.panel1.Width, this.panel1.Height, g1);
            Graphics g2 = Graphics.FromImage(myImage);
            IntPtr dc1 = g1.GetHdc();
            IntPtr dc2 = g2.GetHdc();
            BitBlt(dc2, , , this.panel1.Width, this.panel1.Height, dc1, , , );
            g1.ReleaseHdc(dc1);
            g2.ReleaseHdc(dc2);
            myImage.Save(@"NewImage.bmp ", ImageFormat.Bmp);