Ok, i figured it out. Looks like Xamarin can occasionally lose the connection with a view thats created with a IntPtr.

So instead, we should just store off the ptr:

IntPtr _prevSelectedDayViewPtr;

if (_prevSelectedDayViewPtr != null) {

                UIView prevDayView = new UIView (_prevSelectedDayViewPtr);
                prevDayView.BackgroundColor = UIColor.Clear;
            }


            UIView multiMonthView = (UIView)calView.ValueForKey (new NSString("_monthView"));

            IntPtr dateInfoPtr =  Messaging.IntPtr_objc_msgSend_IntPtr_IntPtr ((new Class ("DateInfo")).Handle, (new Selector (new NSString ("resolveInfoForDate:usingCalendarView:"))).Handle, date.Handle, calView.Handle);
            IntPtr monthViewPtr = Messaging.IntPtr_objc_msgSend_IntPtr (multiMonthView.Handle, new Selector ("resolveMonthViewForDate:").Handle, dateInfoPtr);
            IntPtr monthViewDayPtr = Messaging.IntPtr_objc_msgSend_IntPtr (monthViewPtr, new Selector ("resolveMonthViewDayForDate:").Handle, dateInfoPtr);

            _prevSelectedDayViewPtr = monthViewDayPtr;

            UIView day = new UIView (monthViewDayPtr);    

            day.BackgroundColor = UIColor.Orange;

-SteveZ 

Hey Paul, 

I went back and played around with it again, and I was able to reproduce it. 

I'll try and figure out whats going on and get back to you. 

-SteveZ

Hi Paul, 

I was playing around with the code snippet i posted, and its not reproducing on my end. 

As long as you're not losing  _prevSelectedDayView then you'll always be able reset it. Can you validate that  _prevSelectedDayView is not getting set to null somewhere? If you were to lose that value, then i could see it sticking, but that would be the only case. That view object is only created once when the control is created, so it wouldn't be getting lost on the control side.

-SteveZ

We use this code (the xamarin version) in our application, however there seems to be a defect.  Occasionally, if you tap several cells the colour seems to "stick" so we end up with two or more highlighted cells. Could you let me know if there's a resolution for this, or if it's a known defect and when there will be a fix available?

Thanks 

Hi Michael, 

Sure! I meant to do that originally, but when from your last reply, I just assumed you got it working: 

using MonoTouch.ObjCRuntime;

    public class CalViewDelegate :IGCalendarViewDelegate
    {
        UIView _prevSelectedDayView;
        public override bool MonthViewDayTapped (IGCalendarView calView, NSDate date)
        {
            if (_prevSelectedDayView != null)
                _prevSelectedDayView.BackgroundColor = UIColor.Clear;

            UIView multiMonthView = (UIView)calView.ValueForKey (new NSString("_monthView"));

            IntPtr dateInfoPtr =  Messaging.IntPtr_objc_msgSend_IntPtr_IntPtr ((new Class ("DateInfo")).Handle, (new Selector (new NSString ("resolveInfoForDate:usingCalendarView:"))).Handle, date.Handle, calView.Handle);
            IntPtr monthViewPtr = Messaging.IntPtr_objc_msgSend_IntPtr (multiMonthView.Handle, new Selector ("resolveMonthViewForDate:").Handle, dateInfoPtr);
            IntPtr monthViewDayPtr = Messaging.IntPtr_objc_msgSend_IntPtr (monthViewPtr, new Selector ("resolveMonthViewDayForDate:").Handle, dateInfoPtr);

            _prevSelectedDayView = new UIView (monthViewDayPtr);

            _prevSelectedDayView.BackgroundColor = UIColor.Orange;

            return false;
        }
    }

-SteveZ