How to pass a list of objects to a new window by reference

I'm trying to send a list of objects to a new window by reference, but get a compiler error saying my new window "does not contain a constructor that takes '1' arguments"

Here's my constructor in the new window:
private Options(ref List<Data> _DataList)

And the code that calls it:
Options OptionsWindow = new Options(ref DataList);

What's going on? How do I pass a list of objects to a new window?

re: How to pass a list of objects to a new window by reference

Figured it out...... hope I didn't waste anyone's time on this one.