Check a IList changed?

I am trying to make 开发者_StackOverflow社区an appointment book in Silverlight with C#, so I will have a main AppointmentBook control, with follows to store each of the Appointment control:

    List<kAppointment> appointments = null;

    public IList<kAppointment> Appointments
    {
        get
        {
            if (appointments == null)
            {
                appointments = new List<kAppointment>();
            }

            // Can notify something change here, 
            return appointments;
        }
    }

I can notify the AppointmentBook control new list assigned with above code, so it will redraw each of the appointments control.

But how can I check it if the appointment list is changed by the follows?:

appointments.Add(NewAppointment);

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Sounds like a job for ObservableCollection.

This lets us subscribe to events and tells us in what way the collection changed.

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You can use and ObservableCollection like the others suggest or you can do some encapsulation and not provide complete access to a private member.

If the Add is done through a single public method that you provide you will always know when users of the class are adding appointments and act accordingly.

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I can think of a few things.

1. Make a wrapperclass for the IList that contains an extra boolean changed.
2. Use some variable (a boolean for instance) that you make true when you do an add/remove/edit action, and make it false again when you did the redraw.
3. Keep a copy of the list your're drawing (or only of some index that are present) and check if the 'incoming' and 'last drawed' list are the same
4. Use an ObservableCollection