Why interactions DataTrigger doesn't take effect at design-time?

Assume we have a UserControl containing a DP to control some aspects in the GUI. (e.g. to change color or size of an element, etc)

Which approach is the best?

1. Using DP PropertyChangedCallback

   Through this way, we use code-behind to apply our desired changes (e.g. beginning a storyboard, etc) but we can watch all effects due to any change in DP value even at design-time.

2. Using DataTrigger

   We don't need to use code-behind but we cannot trace changes at design-time. (Can you?)

3. None of them! You have another idea!