An easy way to restrict user to insert more than one appointment for a day is to use the OnFromCreating event handler:
1. When you double click on a time slot the RadScheduler FormCreating
will be fired.
2. The e.Appointment will have start and end time of the clicked time slot.
3. Once you have the appointment start time ( respectively this is the clicked time slot start time) you know for which date user is trying to insert an appointment.
4. The RadScheduler GetAppointmentsEnclosingRange
method retrieve all appointments enclosed in the range. This way you can check if there are any appointments scheduled for this specific day.
5. If there are already - you can set e.Cancel = true and prevent showing the advanced from.
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