Display and edit an array in an editor window?

I have search for a solution to displaying and editing an array for a while but all of the "answers" don't seem to work anymore. So my question is how can i achieve this. I have tried using the solution found here: http://answers.unity3d.com/questions/859554/editorwindow-display-array-dropdown.html

but it throws and error i managed to fix said error but then the window doesn't open at all. Thanks in advance :)