MVVM architecture WPF

I have a little architecture problem with MVVM in WPF. I am having View which contains option to write some code or scan QRCode with computers camera. If user choose to not scan the code, I can bindCommand` and there is no problem.

Problem is there when user choose to scan qrcode. When user press scan code part of screen is being collapsed and camera shows on the screen. I have to do it in View code behind, so the code I am getting in View which is not good in MVVM.

Here how View`s code look like:

private void Scan_Click(object sender, RoutedEventArgs e)
        {
            if (_finalVideo.IsRunning)
            {
                _finalVideo.Stop();
            }

            _finalVideo = new VideoCaptureDevice(_cameraDevices[CamerasList.SelectedIndex].MonikerString);

            _finalVideo.NewFrame += (s, a) =>
            {
                try
                {
                    System.Drawing.Image img = (Bitmap)a.Frame.Clone();
                    var ms = new MemoryStream();
                    img.Save(ms, ImageFormat.Bmp);
                    ms.Seek(0, SeekOrigin.Begin);
                    var bitmapImage = new BitmapImage();
                    bitmapImage.BeginInit();
                    bitmapImage.StreamSource = ms;
                    bitmapImage.EndInit();
                    bitmapImage.Freeze();
                    Dispatcher.BeginInvoke(new ThreadStart(() =>
                    {
                        CameraStream.Source = bitmapImage;
                        ReadQrCode(bitmapImage);
                    }));
                }
                catch
                {
                    //exc
                }
            };

            _finalVideo.Start();
        }

How I can solve that problem with MVVM?