渲染后处理Flowdocument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);
            }

上面的代码没有发布任何内容。一旦flowdocument被分页并且获取了页面的可视化表示，则流式文档的内容将由Visual引用。所以Visual都没有被处理掉，也没有文件的内容。 上面的代码连续执行时会增加内存。

有谁知道如何释放所有这些资源所拥有的内存？

提前致谢。