不使用ShowDialog进行打印将显示空白页

Question

I am experiencing an odd issue with printing from a WPF project. I'm printing a screen capture of the application for reporting purposes, and all that works just fine. Currently the user presses print, the print dialog appears, and they print out the capture image.

However, I want to be able to print directly to the default printer without showing the dialog box. This should be easily done by commenting out the ShowDialog() statement and allowing the rest to just happen. The printer still prints, but the pages are always blank. Can anyone explain this behavior?

private void PrintCurrentScreen()
{
    PrintDialog PD = new PrintDialog();
    PD.PrintTicket.OutputColor = OutputColor.Grayscale;
    PD.PrintTicket.OutputQuality = OutputQuality.Draft;

    PrintTicket PT = new PrintTicket();
    PT.PageOrientation = PageOrientation.Landscape;
    PT.CopyCount = 1;
    PT.PageBorderless = System.Printing.PageBorderless.Borderless;

    //---Blank pages print when commented out---//
    //if (PD.ShowDialog() == true)
    //{
    PD.PrintTicket = PT;

    DrawingVisual DV = new DrawingVisual();
    DV.Offset = new Vector(20, 20);
    DrawingContext DC = DV.RenderOpen();
    DC.DrawImage(previewimage.Source, new Rect(new Size(PD.PrintableAreaWidth - 40, PD.PrintableAreaHeight - 40)));
    DC.Close();

    PD.PrintVisual(DV, "TEST");
    //}
}

Answer 1

Try doing a Measure, Arrange, and UpdateLayout right before the printvisual, like this:

DV.Measure(new System.Windows.Size(PD.PrintableAreaWidth,
              PD.PrintableAreaHeight));
DV.Arrange(new System.Windows.Rect(new System.Windows.Point(0, 0),
              DV.DesiredSize));

DV.UpdateLayout();
PD.PrintVisual(DV, "TEST");