FirstResponder Extension

public static class Extensions
 {
  public static UIView FirstResponder (this UIView view)
  {
   if (view.IsFirstResponder)
    return view;
   foreach (var child in view.Subviews)
   {
    var fs = child.FirstResponder ();
    if (fs != null)
     return fs;
   }
   return null;
  }
 
 }

KeyboardMessGist

		public override void ViewWillDisappear (bool animated)
		{
			base.ViewWillDisappear (animated);
			UnregisterNotifications ();
		}

		public override void ViewWillAppear (bool animated)
		{
			base.ViewWillAppear (animated);
			this.scrollView.ContentSize = new SizeF (320, 400);
			RegisterNotifications ();

		}


		NSObject _keyboardWillShow;
		NSObject _keyboardWillHide;

		protected  void RegisterNotifications ()
		{
			_keyboardWillShow = NSNotificationCenter.DefaultCenter.AddObserver (UIKeyboard.WillShowNotification, WillShow);
			_keyboardWillHide = NSNotificationCenter.DefaultCenter.AddObserver (UIKeyboard.WillHideNotification, WillHide);
		}

		protected  void UnregisterNotifications ()
		{
			NSNotificationCenter.DefaultCenter.RemoveObserver (_keyboardWillShow);
			NSNotificationCenter.DefaultCenter.RemoveObserver (_keyboardWillHide);
		}

		 



		protected  void WillShow (NSNotification notification)
		{
			var activeView = this.View.FirstResponder ();
			if (activeView == null)
				return;			 

			//get keyboard bounds
			var keyboardBounds = UIKeyboard.FrameBeginFromNotification (notification);

			var contentInsets = new UIEdgeInsets (0.0f, 0.0f, keyboardBounds.Size.Height, 0.0f);
			scrollView.ContentInset = contentInsets;
			scrollView.ScrollIndicatorInsets = contentInsets;
			 
			//get the are above the keyboard
			var areaVisibleAboveKeyboard = new RectangleF (this.View.Frame.Location,
				 new SizeF (this.View.Frame.Width, this.View.Frame.Size.Height - keyboardBounds.Size.Height));

			//get the area of the view we want to ensure its visible
			var areaActiveView = activeView.Superview.ConvertRectToView (activeView.Frame, this.View);		 
			 
			//if we can't see the full view, then scroll so its visible
			if (!areaVisibleAboveKeyboard.Contains (areaActiveView)) 
			{
				var scrollPoint = new PointF (0.0f, areaActiveView.Location.Y + areaActiveView.Height + 
					scrollView.ContentOffset.Y - areaVisibleAboveKeyboard.Height);
				scrollView.SetContentOffset (scrollPoint, true);
			}
		}

		protected  void WillHide (NSNotification notification)
		{
			var activeView = this.View.FirstResponder ();
			if (activeView == null)
				return;			  			 

			//scroll back 
			var animationDuration = UIKeyboard.AnimationDurationFromNotification (notification);
			var contentInsets = new UIEdgeInsets (0.0f, 0.0f, 0.0f, 0.0f);
			UIView.Animate (animationDuration, delegate {
				scrollView.ContentInset = contentInsets;
				scrollView.ScrollIndicatorInsets = contentInsets;
			}
			);
		}