Monkeybread Software - DynaPDF Manual

DynaPDF Manual - Page 39

Language Bindings

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It is not clear why this exception occurs, it seems that this is a general bug in the event handling

of Visual Basic 6.0 and VB .Net. A native programming language like C/C++ or Delphi would

never cause an access violation or exception here.

However, to avoid such problems check whether the function is still running:

Private WithEvents FPDF As CPDF 'Enable event support

Private FRunning As Boolean

Private Sub Command1_Click(ByVal eventSender As System.Object, ByVal

eventArgs As System.EventArgs) Handles Command1.Click

If FRunning Then Exit Sub 'Check whether a previous call is running

FRunning = True

'Call some DynaPDF functions here...

DoEvents 'Process messages

FRunning = False

End Sub

The code above checks whether a previous call of the function is running before the function

can be executed again. A quite simple but effective solution that makes your application stabile.

Example (Visual Basic .Net):

Private WithEvents FPDF As CPDF 'Enable event support

Private Sub Form1_Load(ByVal eventSender As System.Object, ByVal

eventArgs As System.EventArgs) Handles MyBase.Load

' We hold one instance of the class CPDF in memory

FPDF = New CPDF()

End Sub

Private Sub Command1_Click(ByVal eventSender As System.Object, ByVal

eventArgs As System.EventArgs) Handles Command1.Click

FPDF.CreateNewPDFA("c:/vbout.pdf")

FPDF.SetDocInfoA(CPDF.TDocumentInfo.diAuthor, "Jens Boschulte")

FPDF.SetDocInfoA(CPDF.TDocumentInfo.diSubject, "My first VB output")

FPDF.SetDocInfoA(CPDF.TDocumentInfo.diTitle, "My first VB output")

FPDF.Append()

' The data type TFStyle is defined in DynaPDFInt.vb

FPDF.SetFontA("Arial", TFStyle.fsItalic, 30.0, True, CPDF.TCodepage.cp1252)

FPDF.WriteFTextA(CPDF.TTextAlign.taCenter, "My first VB .Net output")

FPDF.EndPage()

FPDF.CloseFile()

End Sub

' Error event procedure

Private Sub FPDF_PDFError(ByVal Description As String, ByVal ErrType

As Integer, ByRef DoBreak As Boolean) Handles FPDF.PDFError

DoBreak = (MsgBox(Description, _