Setting PageOrientation for the Wpf DocumentViewer PrintDialog

Mike's answer works. The way I chose to implement it was to instead create my own doc viewer derived from DocumentViewer. Also, casting the Document property to FixedDocument wasn't working for me - casting to FixedDocumentSequence was.

GetDesiredPageOrientation is whatever you need it to be. In my case, I'm inspecting the first page's dimensions, because I generate documents that are uniform size and orientation for all pages in the document, and with only one doc in the sequence.

using System;using System.Collections.Generic;using System.Text;using System.Windows.Controls;using System.Windows.Xps;using System.Printing;using System.Windows.Documents;public class MyDocumentViewer : DocumentViewer{    protected override void OnPrintCommand()    {        // get a print dialog, defaulted to default printer and default printer's preferences.        PrintDialog printDialog = new PrintDialog();        printDialog.PrintQueue = LocalPrintServer.GetDefaultPrintQueue();        printDialog.PrintTicket = printDialog.PrintQueue.DefaultPrintTicket;        // get a reference to the FixedDocumentSequence for the viewer.        FixedDocumentSequence docSeq = this.Document as FixedDocumentSequence;        // set the default page orientation based on the desired output.        printDialog.PrintTicket.PageOrientation = GetDesiredPageOrientation(docSeq);        if (printDialog.ShowDialog() == true)        {            // set the print ticket for the document sequence and write it to the printer.            docSeq.PrintTicket = printDialog.PrintTicket;            XpsDocumentWriter writer = PrintQueue.CreateXpsDocumentWriter(printDialog.PrintQueue);            writer.WriteAsync(docSeq, printDialog.PrintTicket);        }    }}

The workaround I used to set the orientation on my DocumentViewer's print dialog was to hide the print button on the DocumentViewer control by omitting the button from the template. I then provided my own print button and tied it to the following code:

public bool Print()    {        PrintDialog dialog = new PrintDialog();        dialog.PrintQueue = LocalPrintServer.GetDefaultPrintQueue();        dialog.PrintTicket = dialog.PrintQueue.DefaultPrintTicket;        dialog.PrintTicket.PageOrientation = PageOrientation.Landscape;        if (dialog.ShowDialog() == true)        {            XpsDocumentWriter writer = PrintQueue.CreateXpsDocumentWriter(dialog.PrintQueue);            writer.WriteAsync(_DocumentViewer.Document as FixedDocument, dialog.PrintTicket);            return true;        }        return false;    }