protected override bool ControlProc(IntPtr hWndParent, IntPtr hWndControl, int controlId, uint command, IntPtr wParam, IntPtr lParam) { bool handled = false; switch (command) { case 0: uint check = User32.IsDlgButtonChecked(hWndParent, controlId); if (check == 1) { User32.CheckDlgButton(hWndParent, controlId, 0); } else { User32.CheckDlgButton(hWndParent, controlId, 1); } handled = true; break; default: handled = base.ControlProc(hWndParent, hWndControl, controlId, command, wParam, lParam); break; } return(handled); }