private void SetSessionBackground (UINavigationBar navigationBar)
{
var version = Convert.ToDecimal (UIDevice.CurrentDevice.SystemVersion.Split ('.').First ());
if (version >= 7) {
navigationBar.SetBackgroundImage (UIImage.FromFile ("images/SessionsHeader3.png"), UIBarMetrics.Default);
} else if (version >= 5) {
navigationBar.SetBackgroundImage (UIImage.FromFile ("images/SessionsHeader2.png"), UIBarMetrics.Default);
} else {
navigationBar.InsertSubview (new UIImageView (UIImage.FromFile ("images/SessionsHeader2.png")), 0);
}
}