Hi Muniappan S,
I found the error. When we try to open the calendar in the navigation page or popup page (Rg.Popup), it throws an error. The problem disappears when we do Navigation.PushAsync normally.
It should be checked by looking at other page filling events. (NavigationPage, Page, PopupPage).
No Problem :
await Navigation.PushAsync(calendarPopupView);
There is a problem :
await RootPage.Detail.Navigation.PushPopupAsync(calendarPopup);