如何在打印预览界面显示多页，如何在UWP app中打印所有页面？

using Windows.Graphics.Printing;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Printing;

public sealed partial class MainPage : Page
{
    private PrintDocument printDocument;
    private PrintManager printManager;

    public MainPage()
    {
        this.InitializeComponent();
        this.Loaded += MainPage_Loaded;
    }

    private void MainPage_Loaded(object sender, RoutedEventArgs e)
    {
        printManager = PrintManager.GetForCurrentView();
        printManager.PrintTaskRequested += PrintManager_PrintTaskRequested;
    }

    private void PrintManager_PrintTaskRequested(PrintManager sender, PrintTaskRequestedEventArgs args)
    {
        PrintTask printTask = args.Request.CreatePrintTask("Print Task", OnPrintTaskSourceRequested);
    }

    private void OnPrintTaskSourceRequested(PrintTaskSourceRequestedArgs args)
    {
        args.SetSource(printDocument?.DocumentSource);
    }

    private void PrintButton_Click(object sender, RoutedEventArgs e)
    {
        printDocument = new PrintDocument();
        printDocument.Paginate += PrintDocument_Paginate;
        printDocument.GetPreviewPage += PrintDocument_GetPreviewPage;
        printDocument.AddPages += PrintDocument_AddPages;

        PrintManager.ShowPrintUIAsync();
    }

    private void PrintDocument_Paginate(object sender, PaginateEventArgs e)
    {
        printDocument.SetPreviewPageCount(1, PreviewPageCountType.Final);
    }

    private void PrintDocument_GetPreviewPage(object sender, GetPreviewPageEventArgs e)
    {
        printDocument.SetPreviewPage(e.PageNumber, PrintPreviewPageCollection.Current.GetPreviewPage(e.PageNumber - 1));
    }

    private void PrintDocument_AddPages(object sender, AddPagesEventArgs e)
    {
        printDocument.AddPage(PrintPage);
        printDocument.AddPagesComplete();
    }

    private void PrintPage(object sender, AddPagesEventArgs e)
    {
        // 在此处绘制每一页的内容
        // 使用PrintPageEventArgs提供的打印区域信息和页码来绘制内容
    }
}