INotifyPropertyChanged

using System.ComponentModel;
...
    public class foo : INotifyPropertyChanged
    {
        private int _bar;
        public int bar
        {
            get { return _bar; }
            set { _bar = value; if (PropertyChanged != null) OnPropertyChanged("bar"); }
        }

        #region INotifyPropertyChanged Members
        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged(string str)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(str));
            }
        }
        #endregion
    }