можно ловить notification от биндинга

 public abstract class ViewModel : INotifyPropertyChanged
    {
        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        protected void InvokePropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;
            if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
        }

        #endregion
    }

    public partial class MainView : UserControl
    {
        public MainView(MainViewModel model)
        {
            InitializeComponent();
            this.Loaded += (s, e) =>
                               {
                                   this.DataContext = model;
                                   model.PropertyChanged += OnPropertyChanged;
                               };
        }
        protected void OnPropertyChanged(Object obj, PropertyChangedEventArgs args)
        {
            string s = args.ToString();
        }
    }