How to access data and customtype in Basemessage?

Hi. i want to display chat from basemessage by customtype but i can’t access it.

I can access message of Data or Customtype when declare like this.

public List normalChat = new List();
normalChat[i].DATA, normalChat[i].CustomType

but i cannot access them if declare like this

public List normalChatMessage = new List();
normalChatMessage [i].DATA, normalChatMessage [i].CustomType

are there any way can access BaseMessage’s Data or Customtype?

I saved whole Basemessage on member list when use LoadHistory with queryresult. and i wanna display messages from member list using Data and Cutomtype