How do I find if a line intersects a closed line (polygon)?

I have one closed Polyline: "rectangle" and an open Polyline: "line".
Both Polylines may be Z aware.
What is the best way to find if the "line" intersects the "rectangle" in the XY plane?
That is I want a 2D (XY) test for intersection. I do not need the actual coordinates of any intersection(s).