VB.Net Merge multiple pdfs into one and export - vb.net

Question

I have to merge multiple PDFs into a single PDF.
I am using the iText.sharp library, and collect converted the code and tried to use it (from here)
The actual code is in C# and I converted that to VB.NET.
Private Function MergeFiles(ByVal sourceFiles As List(Of Byte())) As Byte()
Dim mergedPdf As Byte() = Nothing
Using ms As New MemoryStream()
Using document As New Document()
Using copy As New PdfCopy(document, ms)
document.Open()
For i As Integer = 0 To sourceFiles.Count - 1
Dim reader As New PdfReader(sourceFiles(i))
' loop over the pages in that document
Dim n As Integer = reader.NumberOfPages
Dim page As Integer = 0
While page < n
page = page + 1
copy.AddPage(copy.GetImportedPage(reader, page))
End While
Next
End Using
End Using
mergedPdf = ms.ToArray()
End Using
End Function
I am now getting the following error:
An item with the same key has already been added.
I did some debugging and have tracked the problem down to the following lines:
copy.AddPage(copy.GetImportedPage(reader,
copy.AddPage(copy.GetImportedPage(reader, page)))
Why is this error happening?

Answer 1

I have a console that monitors individual folders in a designated folder then needs to merge all of the pdf's in that folder into a single pdf. I pass an array of file paths as strings and the output file i would like.
This is the function i use.
Public Shared Function MergePdfFiles(ByVal pdfFiles() As String, ByVal outputPath As String) As Boolean
Dim result As Boolean = False
Dim pdfCount As Integer = 0 'total input pdf file count
Dim f As Integer = 0 'pointer to current input pdf file
Dim fileName As String
Dim reader As iTextSharp.text.pdf.PdfReader = Nothing
Dim pageCount As Integer = 0
Dim pdfDoc As iTextSharp.text.Document = Nothing 'the output pdf document
Dim writer As PdfWriter = Nothing
Dim cb As PdfContentByte = Nothing
Dim page As PdfImportedPage = Nothing
Dim rotation As Integer = 0
Try
pdfCount = pdfFiles.Length
If pdfCount > 1 Then
'Open the 1st item in the array PDFFiles
fileName = pdfFiles(f)
reader = New iTextSharp.text.pdf.PdfReader(fileName)
'Get page count
pageCount = reader.NumberOfPages
pdfDoc = New iTextSharp.text.Document(reader.GetPageSizeWithRotation(1), 18, 18, 18, 18)
writer = PdfWriter.GetInstance(pdfDoc, New FileStream(outputPath, FileMode.OpenOrCreate))
With pdfDoc
.Open()
End With
'Instantiate a PdfContentByte object
cb = writer.DirectContent
'Now loop thru the input pdfs
While f < pdfCount
'Declare a page counter variable
Dim i As Integer = 0
'Loop thru the current input pdf's pages starting at page 1
While i < pageCount
i += 1
'Get the input page size
pdfDoc.SetPageSize(reader.GetPageSizeWithRotation(i))
'Create a new page on the output document
pdfDoc.NewPage()
'If it is the 1st page, we add bookmarks to the page
'Now we get the imported page
page = writer.GetImportedPage(reader, i)
'Read the imported page's rotation
rotation = reader.GetPageRotation(i)
'Then add the imported page to the PdfContentByte object as a template based on the page's rotation
If rotation = 90 Then
cb.AddTemplate(page, 0, -1.0F, 1.0F, 0, 0, reader.GetPageSizeWithRotation(i).Height)
ElseIf rotation = 270 Then
cb.AddTemplate(page, 0, 1.0F, -1.0F, 0, reader.GetPageSizeWithRotation(i).Width + 60, -30)
Else
cb.AddTemplate(page, 1.0F, 0, 0, 1.0F, 0, 0)
End If
End While
'Increment f and read the next input pdf file
f += 1
If f < pdfCount Then
fileName = pdfFiles(f)
reader = New iTextSharp.text.pdf.PdfReader(fileName)
pageCount = reader.NumberOfPages
End If
End While
'When all done, we close the document so that the pdfwriter object can write it to the output file
pdfDoc.Close()
result = True
End If
Catch ex As Exception
Return False
End Try
Return result
End Function

Answer 2

the code that was marked correct does not close all the file streams therefore the files stay open within the app and you wont be able to delete unused PDFs within your project
This is a better solution:
Public Sub MergePDFFiles(ByVal outPutPDF As String)
Dim StartPath As String = FileArray(0) ' this is a List Array declared Globally
Dim document = New Document()
Dim outFile = Path.Combine(outPutPDF)' The outPutPDF varable is passed from another sub this is the output path
Dim writer = New PdfCopy(document, New FileStream(outFile, FileMode.Create))
Try
document.Open()
For Each fileName As String In FileArray
Dim reader = New PdfReader(Path.Combine(StartPath, fileName))
For i As Integer = 1 To reader.NumberOfPages
Dim page = writer.GetImportedPage(reader, i)
writer.AddPage(page)
Next i
reader.Close()
Next
writer.Close()
document.Close()
Catch ex As Exception
'catch a Exception if needed
Finally
writer.Close()
document.Close()
End Try
End Sub

Answer 3

I realize I'm pretty late to the party, but after reading the comments from #BrunoLowagie, I wanted to see if I could put something together myself that uses the examples from his linked sample chapter. It's probably overkill, but I put together some code that merges multiple PDFs into a single file that I posted on the Code Review SE site (the post, VB.NET - Error Handling in Generic Class for PDF Merge, contains the full class code). It only merges PDF files right now, but I'm planning on adding methods for additional functionality later.
The "master" method (towards the end of the Class block in the linked post, and also posted below for reference) handles the actual merging of the PDF files, but the multiple overloads provide a number of options for how to define the list of original files. So far, I've included the following features:
The methods return a System.IO.FileInfo object if the merge is successful.
Provide a System.IO.DirectoryInfo object or a System.String identifying a path and it will collect all PDF files in that directory (including sub-directories if specified) to merge.
Provide a List(Of System.String) or a List(Of System.IO.FileInfo) specifying the PDFs you want to merge.
Identify how the PDFs should be sorted before the merge (especially useful if you use one of the MergeAll methods to get all PDF files in a directory).
If the specified output PDF file already exists, you can specify whether or not you want to overwrite it. (I'm considering adding the "ability" to automatically adjust the output PDF file's name if it already exists).
Warning and Error properties provide a way to get feedback in the calling method, whether or not the merge is successful.
Once the code is in place, it can be used like this:
Dim PDFDir As New IO.DirectoryInfo("C:\Test Data\PDF\")
Dim ResultFile As IO.FileInfo = Nothing
Dim Merger As New PDFManipulator
ResultFile = Merger.MergeAll(PDFDir, "C:\Test Data\PDF\Merged.pdf", True, PDFManipulator.PDFMergeSortOrder.FileName, True)
Here is the "master" method. As I said, it's probably overkill (and I'm still tweaking it some), but I wanted to do my best to try to make it work as effectively as possible. Obviously it requires a Reference to the itextsharp.dll for access to the library's functions.
I've commented out the references to the Error and Warning properties of the class for this post to help reduce any confusion.
Public Function Merge(ByVal PDFFiles As List(Of System.IO.FileInfo), ByVal OutputFileName As String, ByVal OverwriteExistingPDF As Boolean, ByVal SortOrder As PDFMergeSortOrder) As System.IO.FileInfo
Dim ResultFile As System.IO.FileInfo = Nothing
Dim ContinueMerge As Boolean = True
If OverwriteExistingPDF Then
If System.IO.File.Exists(OutputFileName) Then
Try
System.IO.File.Delete(OutputFileName)
Catch ex As Exception
ContinueMerge = False
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("Could not delete existing output file.")
Throw
End Try
End If
End If
If ContinueMerge Then
Dim OutputPDF As iTextSharp.text.Document = Nothing
Dim Copier As iTextSharp.text.pdf.PdfCopy = Nothing
Dim PDFStream As System.IO.FileStream = Nothing
Dim SortedList As New List(Of System.IO.FileInfo)
Try
Select Case SortOrder
Case PDFMergeSortOrder.Original
SortedList = PDFFiles
Case PDFMergeSortOrder.FileDate
SortedList = PDFFiles.OrderBy(Function(f As System.IO.FileInfo) f.LastWriteTime).ToList
Case PDFMergeSortOrder.FileName
SortedList = PDFFiles.OrderBy(Function(f As System.IO.FileInfo) f.Name).ToList
Case PDFMergeSortOrder.FileNameWithDirectory
SortedList = PDFFiles.OrderBy(Function(f As System.IO.FileInfo) f.FullName).ToList
End Select
If Not IO.Directory.Exists(New IO.FileInfo(OutputFileName).DirectoryName) Then
Try
IO.Directory.CreateDirectory(New IO.FileInfo(OutputFileName).DirectoryName)
Catch ex As Exception
ContinueMerge = False
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("Could not create output directory.")
Throw
End Try
End If
If ContinueMerge Then
OutputPDF = New iTextSharp.text.Document
PDFStream = New System.IO.FileStream(OutputFileName, System.IO.FileMode.OpenOrCreate)
Copier = New iTextSharp.text.pdf.PdfCopy(OutputPDF, PDFStream)
OutputPDF.Open()
For Each PDF As System.IO.FileInfo In SortedList
If ContinueMerge Then
Dim InputReader As iTextSharp.text.pdf.PdfReader = Nothing
Try
InputReader = New iTextSharp.text.pdf.PdfReader(PDF.FullName)
For page As Integer = 1 To InputReader.NumberOfPages
Copier.AddPage(Copier.GetImportedPage(InputReader, page))
Next page
If InputReader.IsRebuilt Then
'If Warnings Is Nothing Then
' Warnings = New List(Of String)
'End If
'Warnings.Add("Damaged PDF: " & PDF.FullName & " repaired and successfully merged into output file.")
End If
Catch InvalidEx As iTextSharp.text.exceptions.InvalidPdfException
'Skip this file
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("Invalid PDF: " & PDF.FullName & " not merged into output file.")
Catch FormatEx As iTextSharp.text.pdf.BadPdfFormatException
'Skip this file
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("Bad PDF Format: " & PDF.FullName & " not merged into output file.")
Catch PassworddEx As iTextSharp.text.exceptions.BadPasswordException
'Skip this file
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("Password-protected PDF: " & PDF.FullName & " not merged into output file.")
Catch OtherEx As Exception
ContinueMerge = False
Finally
If Not InputReader Is Nothing Then
InputReader.Close()
InputReader.Dispose()
End If
End Try
End If
Next PDF
End If
Catch ex As iTextSharp.text.pdf.PdfException
ResultFile = Nothing
ContinueMerge = False
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("iTextSharp Error: " & ex.Message)
If System.IO.File.Exists(OutputFileName) Then
If Not OutputPDF Is Nothing Then
OutputPDF.Close()
OutputPDF.Dispose()
End If
If Not PDFStream Is Nothing Then
PDFStream.Close()
PDFStream.Dispose()
End If
If Not Copier Is Nothing Then
Copier.Close()
Copier.Dispose()
End If
System.IO.File.Delete(OutputFileName)
End If
Throw
Catch other As Exception
ResultFile = Nothing
ContinueMerge = False
'If Errors Is Nothing Then
' Errors = New List(Of String)
'End If
'Errors.Add("General Error: " & other.Message)
If System.IO.File.Exists(OutputFileName) Then
If Not OutputPDF Is Nothing Then
OutputPDF.Close()
OutputPDF.Dispose()
End If
If Not PDFStream Is Nothing Then
PDFStream.Close()
PDFStream.Dispose()
End If
If Not Copier Is Nothing Then
Copier.Close()
Copier.Dispose()
End If
System.IO.File.Delete(OutputFileName)
End If
Throw
Finally
If Not OutputPDF Is Nothing Then
OutputPDF.Close()
OutputPDF.Dispose()
End If
If Not PDFStream Is Nothing Then
PDFStream.Close()
PDFStream.Dispose()
End If
If Not Copier Is Nothing Then
Copier.Close()
Copier.Dispose()
End If
If System.IO.File.Exists(OutputFileName) Then
If ContinueMerge Then
ResultFile = New System.IO.FileInfo(OutputFileName)
If ResultFile.Length <= 0 Then
ResultFile = Nothing
Try
System.IO.File.Delete(OutputFileName)
Catch ex As Exception
Throw
End Try
End If
Else
ResultFile = Nothing
Try
System.IO.File.Delete(OutputFileName)
Catch ex As Exception
Throw
End Try
End If
Else
ResultFile = Nothing
End If
End Try
End If
Return ResultFile
End Function

Answer 4

Some may have to make a change to the code at "writer = PdfWriter.GetInstance(pdfDoc, New FileStream(outputPath, FileMode.OpenOrCreate))" as iTextSharp may not support
Change to:
Dim fs As IO.FileStream = New IO.FileStream(outputPath, IO.FileMode.Create)
writer = iTextSharp.text.pdf.PdfWriter.GetInstance(pdfDoc, fs)