WPF中获取形状范围

var polygon = new Polygon();
                polygon.Points.Add(new Point(xStart, yStart));
                polygon.Points.Add(new Point(xEnd, yStart));
                polygon.Points.Add(new Point(xEnd, yEnd));
                polygon.Points.Add(new Point(xStart, yEnd));
                polygon.Arrange(new Rect());
                var geom = polygon.RenderedGeometry;


                if (isFullContained)
                {
                    foreach (var cabinet in CurrentDataProvider.CabinetElementList)
                    {
                        if (geom.FillContainsWithDetail(cabinet.CabinetGeometry) == IntersectionDetail.FullyContains)
                        {
                            cabinet.CabinetStatus = CabinetElement.CabinetStatusTypes.Active;
                            isActiveCabinet = true;
                        }
                    }

                    
                }