Question about creating a dropdown list with dynamic values

[ying lcs]

i have a list of object , A. And object A has 2 string attributes: attr1, attr2.

How can i create a dropdown select list by combining the string of
attr1 and string of attr2?

i.e. I want to create a select value option of
[attr1, attr2]  // for each A in the list of A.

Thank you for any help.