当打印到.xps工作正常时，为什么打印到打印机会导致异常？

I have content loaded into a FlowDocument, which has been loaded into a FlowDocumentReader control, acting as a Print Preview style window. I invoke the FlowDocumentReader.Print() method. This opens the print dialog box, listing all printers connected to my PC. I have content loaded into a FlowDocument, whic