Hi Ming Zhao,
You can subscribe to AppointmentEditDialogShowing
this.radScheduler.AppointmentEditDialogShowing +=new EventHandler<AppointmentEditDialogShowingEventArgs>(radScheduler_AppointmentEditDialogShowing);
Then you need to do the following in the event handler:
void radScheduler_AppointmentEditDialogShowing(object sender, AppointmentEditDialogShowingEventArgs e)
e.AppointmentEditDialog = null;
Please feel free to contact us, if you have additional questions.
the Telerik team