AutoCAD .NET :: WP Selection Set From Existing Poly

Basically I want to create a WP selection set from an existing polyline that the user picks.  The selection set should select everything inside of the closed polyline.

Here is what I have so far:
 
Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument Dim acCurDb As Database = acDoc.Database Dim acEd As Editor = DocumentManager.MdiActiveDocument.Editor '' Start a transaction Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction() '' Lock the document Dim [code]........

I cannot seem to get a 3d collection of points from a polyline.  I have tried a few different things like converting the polyline to a polyline3D, but no luck.

My assumptions are that I need to get the collection of vertices from the polyline.  Then, I need a new collection of points to create the Window Polygon.  I pass those points to the Select Window Polygon method to get my selection window.