public static IObservable <PropertyChangedEventArgs> PropertyChangedAsObservable(
this INotifyPropertyChanged notifyPropertyChanged,
string propertyName)
{
if (propertyName == null)
{
throw new ArgumentNullException(nameof(propertyName));
}
return(notifyPropertyChanged
.PropertyChangedAsObservable()
.Where(x => x.PropertyName == propertyName));
}
