Программа падает на Marshal.Copy при попытке сделать скриншот через WinAPI

class Some {
        [DllImport("user32.dll")]
        static extern int GetSystemMetrics(SystemMetric smIndex);
        
        public enum SystemMetric : int {...}
 
        [DllImport("gdi32.dll", EntryPoint = "CreateCompatibleDC", SetLastError = true)]
        static extern IntPtr CreateCompatibleDC([In] IntPtr hdc);
 
        [DllImport("gdi32.dll", EntryPoint = "CreateCompatibleBitmap")]
        static extern IntPtr CreateCompatibleBitmap([In] IntPtr hdc, int nWidth, int nHeight);
 
        [DllImport("gdi32.dll", EntryPoint = "SelectObject")]
        public static extern IntPtr SelectObject([In] IntPtr hdc, [In] IntPtr hgdiobj);
 
        enum TernaryRasterOperations : uint { ... }
 
        [DllImport("gdi32.dll", EntryPoint = "BitBlt", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool BitBlt([In] IntPtr hdc, int nXDest, int nYDest, int nWidth, int nHeight, [In] IntPtr hdcSrc, int nXSrc, int nYSrc, TernaryRasterOperations dwRop);
 
        [DllImport("user32.dll")]
        static extern IntPtr GetDC(IntPtr hWnd);
 
        [DllImport("gdi32.dll", EntryPoint = "DeleteDC")]
        public static extern bool DeleteDC([In] IntPtr hdc);
 
        [DllImport("user32.dll")]
        static extern bool ReleaseDC(IntPtr hWnd, IntPtr hDC);
 
        byte [] screen() {
            int screenHeight = GetSystemMetrics(SystemMetric.SM_CYVIRTUALSCREEN);
            int screenWidth = GetSystemMetrics(SystemMetric.SM_CXVIRTUALSCREEN);
 
            IntPtr hdc = GetDC(IntPtr.Zero);              // get a desktop dc
            IntPtr hDest = CreateCompatibleDC(hdc); // create a dc to use for capture
 
            IntPtr hbCapture = CreateCompatibleBitmap(hdc, screenWidth, screenHeight);
            SelectObject(hDest, hbCapture);
 
            // the following line effectively copies the screen into the capture bitamp
            BitBlt(hDest, 0, 0, screenWidth, screenHeight, hdc, 0, 0, TernaryRasterOperations.SRCCOPY);
 
            // clean up - release unused resources!
            ReleaseDC(IntPtr.Zero, hdc);
            DeleteDC(hDest);
            
            int size = screenWidth * screenHeight; // пробовал так же: screenWidth * screenHeight * 3 или: screenWidth * screenHeight + screenHeight; есть большие подозрения, что косячу именно тут, но как именно - хз
            byte[] managedArray = new byte[size];
            string error;
            try
            {
                Marshal.Copy(hbCapture, managedArray, 0, size); // crush
            }
            catch (Exception ex)
            {
                error = ex.Message;
            }
           
            return managedArray;
      }
}