Xamarin.iOS Blur screen with OnResignActivation

AppDelegate.cs

[Register ("AppDelegate")]
public partial class AppDelegate : UIApplicationDelegate
{
	UIVisualEffectView _blurView = null;

	public override void OnActivated (UIApplication application)
	{
		try {
			if (_blurView != null) {
				_blurView.RemoveFromSuperview ();
				_blurView.Dispose ();
				_blurView = null;
			}	
		} catch {}
	}

	public override void OnResignActivation (UIApplication application)
	{
		// Blur screen
		using (var blurEffect = UIBlurEffect.FromStyle (UIBlurEffectStyle.Light)) {
			_blurView = new UIVisualEffectView (blurEffect);
			_blurView.Frame = _window.RootViewController.View.Bounds;
			_window.RootViewController.View.AddSubview (_blurView);
		}
	}
}