Inheritance: INotifyPropertyChanged, IDisposable
 public ViewModelChangedArgs(ViewModelBase model, string property, object oldValue, object newValue)
 {
     ViewModel = model;
     Property = property;
     OldValue = oldValue;
     NewValue = newValue;
 }
 private void ViewModelBaseOnViewModelChanged(ViewModelBase.ViewModelChangedArgs args)
 {
     if (Theme == null)
         return;
     if (args.ViewModel.GetTag() == Theme.GetTag())
         InvalidateVisual();
 }