private UIView _activeview;
private float _scrollAmount = 0.0f;    // amount to scroll
private float _bottom = 0.0f;           // bottom point
private float _offset = 10.0f;          // extra offset
private bool _moveViewUp = false;

public override void ViewDidLoad()
{
    base.ViewDidLoad();

            // Keyboard popup
            NSNotificationCenter.DefaultCenter.AddObserver
            (UIKeyboard.DidShowNotification, KeyBoardUpNotification);

            // Keyboard Down
            NSNotificationCenter.DefaultCenter.AddObserver
            (UIKeyboard.WillHideNotification, KeyBoardDownNotification);

            UITapGestureRecognizer tapGestureRecognizer = new UITapGestureRecognizer(() =>
            {
                //TODO: also should be good find all fields in View automatically
                NameSurnameField.ResignFirstResponder();
                UsernameField.ResignFirstResponder();
                CountryField.ResignFirstResponder();
                StatusField.ResignFirstResponder();
                EmailField.ResignFirstResponder();
                BirthdayField.ResignFirstResponder();
                GenderField.ResignFirstResponder();
            });
            View.AddGestureRecognizer(tapGestureRecognizer);
}

private void KeyBoardUpNotification(NSNotification notification)
        {
            // get the keyboard size
            CGRect r = UIKeyboard.BoundsFromNotification(notification);

            GetViewThatOpenKeyboard(View);

            if (_activeview == null)
                return;

            CGRect frameRelativeToParent = _activeview.ConvertRectToView(_activeview.Bounds, View);

            _bottom = (float)(frameRelativeToParent.Y + frameRelativeToParent.Height + _offset);

            // Calculate how far we need to scroll
            _scrollAmount = (float)(r.Height - (View.Frame.Size.Height - _bottom));

            // Perform the scrolling
            if (_scrollAmount > 0)
            {
                _moveViewUp = true;
                ScrollTheView(_moveViewUp);
            }
            else
            {
                _moveViewUp = false;
            }
        }

 private void GetViewThatOpenKeyboard(UIView view)
        {
            if (view.IsFirstResponder)
            {
                _activeview = view;
                return;
            }

            foreach (var v in view.Subviews)
                GetViewThatOpenKeyboard(v);
        }

private void KeyBoardDownNotification(NSNotification notification)
        {
            if (_moveViewUp) { ScrollTheView(false); }
        }

private void ScrollTheView(bool move)
        {
            // scroll the view up or down
            UIView.BeginAnimations(string.Empty, IntPtr.Zero);
            UIView.SetAnimationDuration(0.3);

            CGRect frame = View.Frame;

            if (move)
            {
                frame.Y -= _scrollAmount;
            }
            else
            {
                frame.Y += _scrollAmount;
                _scrollAmount = 0;
            }

            View.Frame = frame;
            UIView.CommitAnimations();
        }