Extract 3dpolyline from Featureline

It is possible to extract a polyline from a Featureline here is an example

    Public Function PolylinefromFeatureline(ByVal Featureline As Civil.Land.DatabaseServices.FeatureLine) As Object
        'Refer to this forum post
        'http://forums.autodesk.com/t5/AutoCAD-Civil-3D-Customization/Polylines-from-Featureline/td-p/3313009
        'http://msmvps.com/blogs/joacim/archive/2009/08/31/gettype-and-typeof-confusion.aspx

        Dim cv As Curve = Featureline.BaseCurve

        'The basecurve of a featureline can be a 3dpolyline, 2dpolyline or a curve
        'check if the base curve is a 3dPolyline
        If cv.GetType() Is GetType(Autodesk.AutoCAD.DatabaseServices.Polyline3d) Then
            MsgBox("this is 3dpolyline")
        End If

        'check if the base curve is a Polyline
        If cv.GetType() Is GetType(Autodesk.AutoCAD.DatabaseServices.Polyline) Then
            MsgBox("this is polyline")
        End If

        'check if the base curve is a 2dPolyline
        If cv.GetType() Is GetType(Autodesk.AutoCAD.DatabaseServices.Polyline2d) Then
            MsgBox("this is 2dpolyline")
        End If

        'check if the base curve is a curve
        If cv.GetType() Is GetType(Autodesk.AutoCAD.DatabaseServices.Curve) Then
            MsgBox("this is a curve")
        End If


        Return cv

    End Function