print preview and print in wpf

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C#

WPF

I have a WPF Form ,I need to print it ,i use DocumentViewer to print. but when I want to Print it or Preview , I only See the first page while i have more than one page

private void Print(object sender, RoutedEventArgs e)
{
PrintSettings printSettings = PrintSettings.Default;
UIElement container = this.Content as UIElement;
ScrollViewer containerPanel = Helper.FindVisualChildren<ScrollViewer>(container).FirstOrDefault();
var origParentDirection = containerPanel.FlowDirection;
var origDirection = (containerPanel.Content as FrameworkElement).FlowDirection;
if (containerPanel != null && containerPanel.FlowDirection == FlowDirection.RightToLeft)
{
containerPanel.FlowDirection = FlowDirection.LeftToRight;
(containerPanel.Content as FrameworkElement).FlowDirection = FlowDirection.RightToLeft;
}
var window = new Window();
string tempFileName = System.IO.Path.GetTempFileName();
System.IO.File.Delete(tempFileName);
using (XpsDocument xpsDocument = new XpsDocument(tempFileName, FileAccess.ReadWrite, System.IO.Packaging.CompressionOption.Fast))
{
XpsDocumentWriter writer = XpsDocument.CreateXpsDocumentWriter(xpsDocument);
(containerPanel.Content as FrameworkElement).Margin = new Thickness(20);
writer.Write((containerPanel.Content as FrameworkElement), printSettings.PrintTicket);
var doc = xpsDocument.GetFixedDocumentSequence();
doc.PrintTicket = printSettings.PrintTicket;       
window.FlowDirection = System.Windows.FlowDirection.RightToLeft;
window.Content = new DocumentViewer { Document = doc };
window.Margin = new Thickness(10);
window.ShowDialog();
}
(containerPanel.Content as FrameworkElement).FlowDirection = origDirection;
containerPanel.FlowDirection = origParentDirection;
}