RadScheduler - e.Appointment.BackgroundId property in AppointmentFormatting event does not work correctly, when you open Edit Appointment dialog form to edit the Background color of selected appointment. Steps to reproduce: 1. Subscribe to AppointmentFormatting event and set e.Appointment.BackgroundId property. 2. Create new Appointment via Edit Appointment dialog form. 3. Open the the appointment via Edit Appointment dialog form and change the Background color. 4. Close the Edit Appointment dialog form. Work around: Do not set this property in AppointmentFormatting event. CLOSED: Modifying data properties of the appointment should not be done on the Formatting events. The Formatting events stand for modifying visual properties of the elements being rendered and are fired during element creation. Modifying any data property of the active view or of the appointments will call another element creation cycle recursively and might result in StackOverflow exceptions or ElementAlreadyAdded exceptions.