Hi All, I have a observable collection of viewmodel objects. How can I subscribe to the Property Changed event of each view model in my collection as they are created and track which ones have been changed, so that I can updated them to my database.

//This is how I load my data
    public static ObservableCollection<ProgramViewModel> program { get; set; }
    program = new ObservableCollection<ProgramViewModel>();
    foreach (DomainObject obj in res.ResultSet)
                    {
    Program prg = (Program)obj;
     program.Add(new ProgramViewModel(prg));
    }