Custom transition iOS 7 - ios7

Question

I have been struggling writing a custom transition to present a controller. What I would like to do is to have a side menu (right side), and when user makes a swipe gesture present this controller.
I already wrote a custom transitioning delegate which is presenting the controller, but I would like to dismiss it using the same kind of animation. I have tried and tried, but the controller dismisses with no animation at all, it just disappears.
This is what I have so far, I'm using xamarin IOS:
var container = transitionContext.ContainerView;
var fromViewController = transitionContext.GetViewControllerForKey (UITransitionContext.FromViewControllerKey);
var toViewController = transitionContext.GetViewControllerForKey (UITransitionContext.ToViewControllerKey);
var endingFrame = new RectangleF (66, container.Frame.Y, container.Frame.Width, container.Frame.Height);
var startFrame = new RectangleF (UIScreen.MainScreen.Bounds.Width, 0, 0, container.Frame.Height);
if (Presenting) {
container.AddSubview (fromViewController.View);
container.AddSubview (toViewController.View);
toViewController.View.Frame = startFrame;
UIView.Animate (TransitionDuration (transitionContext), () => {
toViewController.View.Frame = endingFrame;
}, () => {
transitionContext.CompleteTransition (true);
});
} else {
container.AddSubview (fromViewController.View);
container.AddSubview (toViewController.View);
UIView.Animate (TransitionDuration (transitionContext), () => {
fromViewController.View.Frame = startFrame;
}, () => {
transitionContext.CompleteTransition (true);
});
}
I think the problem is with the frames, I don't know if I'm setting them correctly.
please help!!