Forcing OnPropertyChanged to update the UI

Having used my new Func<T, T> friend (see Action<T> and Func<T, TResult>) the bound TextBox refused to show the revised value. Even though OnPropertyChanged("...") had been called the property's "getter" was not called by WPF.

I don't really understand why.

To get round this problem I added a FormattingConverter to the TextBox called DoNothingConverter. Its presence is sufficient to ensure the UI updates.

public class DoNothingConverter : IValueConverter
{
   public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
   {
      return value;
   }
   public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
   {
      return value;
   }
}