Thank you for writing.
I am not sure I completely understand your scenario and I am not sure where you have added your ID property. In case you are using a data source, you can try using the DataItem
property which holds a reference to the corresponding item from the data source. In case you are using custom appointment with an ID property added, you can just cast the appointment to your custom type:
sender, Telerik.WinControls.Data.NotifyCollectionChangedEventArgs e)
(e.Action == Telerik.WinControls.Data.NotifyCollectionChangedAction.ItemChanged)
IEvent appointment = (IEvent)e.NewItems;
id = ((MyDataRowType)appointment.DataItem).ID;
id = ((MyAppointmentType)appointment).ID;
If this is not what you need, please provide more detailed explanation of your requirements and your current implementation. You can also include some code snippets which will let me understand your case better.
Off topic, can you please let me know which version of RadControls for WinForms are you using, since you account shows a trial download from back in 2010.
Please let me know if you need further help.
the Telerik team