Default Drop Down Value when List Retrieve from other Table

Default Drop Down Value when List Retrieve from other Table

Hi, 

I am adding a list from a table for one of my drop down menu using the following method:

 input.DropDown:ui.add(MyList)

But when the list get fetched but there is no default value in the drop down menu until i click the dropdown.

Anyone can give me any pointers?

Best regards,
Soon Joo