CAD VB.net CircularArc3d GetLength

For i As Integer = 0 To myLwPolyline.NumberOfVertices - 1
   Dim segType As SegmentType = myLwPolyline.GetSegmentType(i)
   If segType = SegmentType.Arc Then
      Dim myArc As Autodesk.AutoCAD.Geometry.CircularArc3d = myLwPolyline.GetArcSegmentAt(i)
      myLength = myArc.GetLength(myArc.GetParameterOf(myArc.StartPoint), myArc.GetParameterOf(myArc.EndPoint), 0)
      myRadius = myArc.Radius
   End If
Next