The Secret Rebirth of Visual Basic’s .PrintForm

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If you’ve managed to print anything in .NET, you’ll know it’s no mean task. What, you may ask, happened to the old .PrintForm method of VB6 fame? Unfortunately, like a number of older features, it got sold out in the name of “standardization.”

But don’t fret: With just a few lines of extra code, we can bring it back from the dead. How? Simply follow these four easy steps:

1. Design your form as usual, adding all the required controls you want to be printed.
2. From your Toolbox, add one PictureBox, PrintDocument, and PrintDialog controls to your form. These will all be used by our code to support the printing of your form. For this code sample, I’ve named my controls MyPictureBox, MyPrintDocument, and MyPrintDialog respectively. The PictureBox is the only “visible” control, which you can make invisible if you want.
3. Add the following code behind your form. These functions perform the basic function of taking a screenshot and sending the results to the printer. The main method is PrintForm:

Public Sub PrintForm()
    ' Takes a screenshot, then initiates the print
    GrabScreen()
    MyPrintDialog.Document = MyPrintDocument
    If MyPrintDialog.ShowDialog = DialogResult.OK Then
        MyPrintDocument.Print()
    End If
End Sub

' API call to help generate final screenshot
Private Declare Auto Function BitBlt Lib "gdi32.dll" (ByVal _
    hdcDest As IntPtr, ByVal _
    nXDest As Integer, ByVal nYDest As Integer, ByVal nWidth _
    As Integer, ByVal nHeight _
    As Integer, ByVal hdcSrc As IntPtr, ByVal nXSrc _
    As Integer, _
    ByVal nYSrc As Integer, ByVal dwRop As System.Int32) _
    As Boolean
' Variable to store screenshot
Private bmpScreenshot As Bitmap

Private Sub GrabScreen()
  ' Performs a screenshot, saving results to bmpScreenshot
  Dim objGraphics As Graphics = Me.CreateGraphics
  Dim objSize As Size = Me.Size
  Const SRCCOPY As Integer = &HCC0020

  bmpScreenshot = New Bitmap(objSize.Width, objSize.Height, _
                             objGraphics)
  Dim objGraphics2 As Graphics = _
      objGraphics.FromImage(bmpScreenshot)
  Dim deviceContext1 As IntPtr = objGraphics.GetHdc
  Dim deviceContext2 As IntPtr = objGraphics2.GetHdc

  BitBlt(deviceContext2, 0, 0, Me.ClientRectangle.Width, _
    Me.ClientRectangle.Height, deviceContext1, 0, 0, SRCCOPY)
  objGraphics.ReleaseHdc(deviceContext1)
  objGraphics2.ReleaseHdc(deviceContext2)
End Sub

Private Sub MyPrintDocument_PrintPage(ByVal sender _
  As System.Object, _
  ByVal e As System.Drawing.Printing.PrintPageEventArgs) _
  Handles MyPrintDocument.PrintPage
  ' Method that handles the printing
  Dim objImageToPrint As Graphics = e.Graphics
  objImageToPrint.DrawImage(bmpScreenshot, 0, 0)
  bmpScreenshot.Dispose()
  objImageToPrint.Dispose()
  e.HasMorePages = False
End Sub

4. Add a print button to your control, add code to run the PrintForm method; then simply wait and let our code run its magic! Don’t forget, you may want to make certain controls (such as the print button itself) invisible before running the PrintForm method, then making it visible again afterward.

And that’s quite simply all you need to print your form. Admittedly not as easy as .PrintForm, but when the code is already written and ready-to-roll, who’s complaining?

About the Author

Karl Moore (MCSD, MVP) is an experience author living in Yorkshire, England. He is author of numerous technology books, including the new Ultimate VB .NET and ASP.NET Code Book, plus regularly features at industry conferences and on BBC radio. Moore also runs his own creative consultancy, White Cliff Computing Ltd. Visit his official Web site at www.karlmoore.com.

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