public interface INotifyPropertyChanging {
	event PropertyChangingEventHandler PropertyChanging;
}

public delegate void PropertyChangingEventHandler(object sender,
	PropertyChangingEventArgs e);

public class PropertyChangingEventArgs : EventArgs {
public PropertyChangingEventArgs(string propertyName);
public virtual string PropertyName { get; }
}

public interface INotifyPropertyChanged {
	event PropertyChangedEventHandler PropertyChanged;
}

public delegate void PropertyChangedEventHandler(object sender,
	PropertyChangedEventArgs e);

public class PropertyChangedEventArgs : EventArgs {
public PropertyChangedEventArgs(string propertyName);
public virtual string PropertyName { get; }
}
