I want to use select box on dialog

[select-good-way]

Hi, i want to use select box on dialog , but when I am using it with append-to-body property dropdown getting displayed behind the dialog and also I have increased the z-index but it still behind the dialog , I set append-to-body to false i showing dropdown on dialog properly but my dialog having few fields and drop down getting over flow in side dialog container and getting hide dropdown .
please suggest me how to handle it properly