Hide/Unhide Property and event on drag of activity

Question

I have created a custom activity which contains various InArguments.

I need to hide/unhide  one property based on second property value.

 

That i have achieved through browsable attribute.

But it works fine only for the first time.

Suppose i have changed value of first property (which is dropdown), on that changed value m able to unhide the second property. But when i drag the same activity again , it shows the unhide property by default.

 

This i have wriiten in Cachemetadata function. I want to do this on some event/method which is called whenever that activity is dragged from toolbox or on some event/method which is called when selection of dropdown is changed.