how to add a dropdown menu (only using c# script)?

I just started using Unity for my research project and need to implement a dropdown menu for GUI!
how can I add a dropdown menu (only using c# script)?
I am not sure how I can instantiate the dropdown menu (it’s not even getting displayed…)

My code is as follows for now…
(just trying to display it before starting to implement the backend part):

UnityEngine.UI.Dropdown dropdown;

any help would be greatly appreciated!
Thank you!

1st: Use the new UI system…

2nd: Use the animator, you dont really need a script. Simply create your drop down by an animator.
https://unity3d.com/learn/tutorials/topics/animation