When RadCalendar is inside Xamarin Forms Tabbed Page. Switching between tabs triggers Calendar SelectionChanged and the calendar DisplayDate is changed. 

Workaround:
the issue could not be reproduced when RadTabView is used and its IsContentPreserved property is set to true.

In Xamarin Forms.

When I call Calendar.ScrollAppointmentIntoView(theItem); in Android it works fine.

In iOS when the same call is made, the calendar scrolls about 1 pixel, then stops.

I put the call into a timer just to make sure it's there.

      Device.StartTimer(TimeSpan.FromMilliseconds(3000), () =>    

              { Device.BeginInvokeOnMainThread(() => {  Calendar.ScrollAppointmentIntoView(theItem); });             

                 return false; // True = Repeat again, False = Stop the timer    

      });

It would be handy to enable dates/disable dates based on an array of dates. 

I have a situation where drivers are scheduled jobs that may exclude days within a 3-week period.  Currently I can only select set the minimum and maximum dates for this period which allows them to select dates where no work is scheduled.  Consequently my code must check if the selected date "is valid" before allowing displaying the jobs for the selected date.

Obviously it would be far easier if those dates were never enabled in the first place.

With the current implementation of the control, if you have events later in the day - the user needs to scroll down so that they are shown. We can consider adding a mechanism to show the first available event or expose methods to bring a specific event into view.

Region.Op.REPLACE is deprecated and therefore the exception is thrown:

[AndroidRuntime] java.lang.IllegalArgumentException: Invalid Region.Op - only INTERSECT and DIFFERENCE are allowed
[AndroidRuntime] at android.graphics.Canvas.checkValidClipOp(Canvas.java:779)
[AndroidRuntime] at android.graphics.Canvas.clipRect(Canvas.java:826)
[AndroidRuntime] at com.telerik.widget.calendar.CalendarFragment.drawRows(CalendarFragment.java:589)
[AndroidRuntime] at com.telerik.widget.calendar.CalendarFragment.render(CalendarFragment.java:259)
[AndroidRuntime] at com.telerik.widget.calendar.CalendarScrollManager$FragmentHolder$LayerView.onDraw(CalendarScrollManager.java:136)
[AndroidRuntime] at android.view.View.draw(View.java:20207)

If there is an all-day appointment at a certain date, navigating to a different date through the week navigation in DayView and going back to the previous date, it will not always show the all-day item.

The RadCalendar DayView.EventView get stuck in a shifted position. This only occurs on iOS.

Steps to reproduce:

1. Load calendar.

2. Slowly slide the event view (lower portion) either right or left until the time labels (1am, 2am, etc.) are no longer in their starting positions.

3. Without releasing the scroll, tap the button to change the view to Month view mode.

4. Tap the button to change back to Day view mode.

5. Observe that the entire events view is still shifted and will remain so until the RadCalendar control is destroyed and a new one is created.

Attached are pictures showing the correct view and the incorrect view. Also, a sample project is attached that can be used to replicate this issue.

I have attempted to use a custom renderer to manually reset the events view, but nothing seems to work.

SelectionChanged starts calling twice when appointments collection is changed at runtime from within the event.

The problem occurs when I update the Events property on either of the events DisplayDateChanged or SelectionChanged. It seems these events are triggered another time, sometimes, when the AppointmentSource gets refreshed. I say sometimes because you can navigate through the weeks as normal, but as some points you notice something went wrong. Here’s a list of what I have encountered so far :
When sliding through the weeks from the days header, let’s say the selected day is a Monday, the next weeks would have the Monday selected as expected. Then a random week would have an other selected day (Friday). It would happen randomly until some weeks get skipped completely.
When sliding through the weeks from the days header, let’s say the selected day is a Monday, the next weeks would have the Monday selected as expected. If I touch the Friday box,  the selected date gets initially updated  to Friday and then a random day between Monday and Friday gets selected.
When sliding through the weeks from the days header, the calendar gets stucked on a random week, and sliding forward or backward through the days header just put you back to the same week. In this case the only way to move to the next/previous week is to slide through the time slot.

The Android and iOS versions of the control support multiple and range selections. We should consider embedding such features in the Xamarin.Forms control as well.

Links to the features in iOS and Android:

- Android Range Selection: https://docs.telerik.com/devtools/xamarin/nativecontrols/android/calendar/calendar-selection

- iOS Range Selection: https://docs.telerik.com/devtools/xamarin/nativecontrols/ios/calendar/selection