/// <summary>
 /// Creates a new property helper instance.
 /// </summary>
 /// <param name="onPropertyChanged">Property change notification delegate.</param>
 public CalculatedAsyncPropertyHelper(Action <PropertyChangedEventArgs> onPropertyChanged)
     : base(Adapt(onPropertyChanged))
 {
     this._propertyHelper = new CalculatedProperties.PropertyHelper(onPropertyChanged);
 }
 /// <summary>
 /// Creates a new property helper instance.
 /// </summary>
 /// <param name="onPropertyChanged">Property change notification delegate.</param>
 public CalculatedAsyncPropertyHelper(Action <string> onPropertyChanged)
     : base(onPropertyChanged)
 {
     this._propertyHelper = new CalculatedProperties.PropertyHelper(NotifyPropertyChanged);
 }