pagination - 渲染后处理流文档页面

Question

            //Create a User Control with a TextBlock
            TextBlock textBlock = new TextBlock();
            textBlock.Text = "Helo";
            UserControl userCOntrol = new UserControl();
            userCOntrol.Content = textBlock;

            //Add the UserControl to a Table
            table.RowGroups[0].Rows[0].Cells[0].Blocks.Add(new Paragraph(new InlineUIContainer(userCOntrol as UIElement)));

            //Add the table to a FlowDocument
            FlowDocument flowDocument = new FlowDocument();
            flowDocument.Blocks.Add(table);

            //Fetch the Visual representation of the page.
            DocumentPage page = ((IDocumentPaginatorSource)flowDocument).DocumentPaginator.GetPage(0);


            //Extract the Visual from the page and add to a Fixed Page
            FixedPage fixedPage = new FixedPage();
            ContainerVisual container = new ContainerVisual();
            container.Children.Add(page.Visual);
            DrawingCanvas canvas= new DrawingCanvas();
            canvas.AddVisual(container);
            fixedPage.Children.Add(canvas);


            //now write the FixedPage to an XPS file
            using (XpsDocument xpsDoc = new XpsDocument("c:\\x.xps", FileAccess.ReadWrite))
            {
                XpsDocumentWriter xpsDw = XpsDocument.CreateXpsDocumentWriter(xpsDoc);
                xpsDw.Write(kj);
            }

上面的代码没有释放任何东西。一旦对流文档进行分页并获取页面的视觉表示，则流文档的内容将由 Visual 引用。因此，Visual 和 flowdocument 的内容都不会被处理。上面这段代码在执行时连续出现内存不足。

有谁知道如何释放所有这些资源所持有的内存？

提前致谢。