https://ldcis4e:50001/sap/bc/webdynpro/sf0a0001/dyn_event?sap-language=EN

solution就是每次Add的時候首先動态建立一個新的context node ( with attribute ), 然後再動态建立UI File Upload,建立同時把剛建立的context node一起傳到構造函數裡去,這樣binding就建立好了.
delete attachment時候把context和File Upload一起delete就OK了.