Vikky Vikky - 1 year ago 229 Question

VB.Net Merge multiple pdfs into one and export

I have to merge multiple PDFs into a single PDF.

I am using the 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)
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
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, page)))

Why is this error happening?

Answer Source

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

        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
            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
                    'Create a new page on the output document
                    '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)
                        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
            result = True
        End If
    Catch ex As Exception
        Return False
    End Try
    Return result
End Function