Code behind for full screen camera view

CameraView.cs

public partial class CameraView : PhoneApplicationPage
{
    private PhotoCamera cam;
    public CameraView()
    {
        InitializeComponent();
        activateCamera();
    }

    private void activateCamera()
    {
        //You should do all your camera availability checks here first.
        cam = new PhotoCamera(CameraType.Primary);
        // Event is fired when the PhotoCamera object has been initialized.
        cam.Initialized += cam_Initialized;
            
        //Set the VideoBrush source to the camera.
        viewfinderBrush.SetSource(cam);            
    }

    void cam_Initialized(object sender, CameraOperationCompletedEventArgs e)
    {
        if (e.Succeeded)
        {
            this.Dispatcher.BeginInvoke(delegate()
            {
                // Use the orientation to determine how to transform the camera preview
                previewTransform.Rotation = cam.Orientation ;

                var res = cam.AvailableResolutions.FirstOrDefault();
                //calculate the dimensions of the canvas to match the aspect ratio that the video feed will be displayed in.
                //currently set to max height from xaml, so we need to calculate the width
                viewfinderCanvas.Width = (res.Height / res.Width) * viewfinderCanvas.ActualHeight;
            });
        }
    }
}