Is there a way to suppress the text 'Click to Add Appointment' in the UltraDayView control?
If you mean prevent the thing from appearing altogether, set UltraDayView.ShowClickToAddIndicator to false. If you mean change the text to an empty string, you can do something like the following:
Infragistics.Win.UltraWinSchedule.Resources.Customizer.SetCustomizedString("ClickToAddAppointment_Text", " ");Infragistics.Win.UltraWinSchedule.Resources.Customizer.SetCustomizedString("ClickToAddEvent_Text", " ");