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Exception"Null reference" when converting PDF to HTML(C#)

Aspose.PDF Product Family
#1

When using multiple threads to convert PDFs to other formats (have tested this with Word and HTML), I sporadically get a null reference error:
Error processing C:\Users\steven\Desktop\Demo Results\Processed\Alfreds Futterkiste.pdf: System.NullReferenceException: Object reference not set to an instance of an object.
at System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) at #=z7B66NTNGFA169JLoUmrwKxgD8jaW.#=zrehnqg4=() at #=zjQofK5uQT1nrczm2hqUfn5rTB69qRYYos7w$enU=.#=zc07YwmE=(IList1 #=zXQV4p3t6b6Zw, #=zUXsHvDp_PywOqaOUR5YzYceSxILpMOyVPA== #=zdBORxco=, #=zhEH9Bc_Wang_9YLQVBUdfsZatAgmzuy2AOpUOpg= #=zds9OORg=)
at #=zSkKpsnW4_l8d3oWw$rCKZvnjq_0o.#=zc07YwmE=(String #=zJaRRVAGKJ0$y, #=zhOwO0qGv1_zr7ukGF8zdWlJryxnLBgmyZw== #=zds9OORg=, IList`1 #=zXQV4p3t6b6Zw, #=zElZS3rTNPGRb2G8bbB096HjlemU26jn78oFyxoU= #=z1Un$IH4=, #=zoJ0W652CgKjIWtgorYMNb57mwf5e #=zDppDFBU8JVcJ)
at #=zMYqbptfeeqhc6FkgO9qM6Ug=.#=zB9de9gE=(Document #=zgdQy3nA=, String #=zx6UtPYJ33E_xuAIJOw==, Stream #=z2fSaFZn_yKhE, HtmlSaveOptions #=zds9OORg=)
at Aspose.Pdf.Document.#=zEszYJEKR61hZ(String #=zJaRRVAGKJ0$y, SaveOptions #=zds9OORg=)
at Aspose.Pdf.Document.Save(String outputFileName, SaveOptions options)
at All_About_PDF.PDFConverter.convertPDFToHTML(String file, String outputFolder, String password, Boolean zipResult) in PDFConverter.cs:line 257
at All_About_PDF.PDFConverter.<>c__DisplayClass3_0.b__0(String file) in PDFConverter.cs:line 99

This occurs when I put the conversion in Parallel.ForEach with 4 threads.

#2

@amani7,

Thanks for contacting support.

Can you please share source files along with sample code so that we may further investigate to help you out.

#3 
    static string convertPDFToWord(string file, string outputFolder, string password = "")
    {
        string outputFile = System.IO.Path.Combine(outputFolder, System.IO.Path.GetFileNameWithoutExtension(file) + ".docx");

        using (Aspose.Pdf.Document doc = new Aspose.Pdf.Document(file, password))
        {
            Aspose.Pdf.DocSaveOptions saveOptions = new Aspose.Pdf.DocSaveOptions();
            saveOptions.Mode = Aspose.Pdf.DocSaveOptions.RecognitionMode.Flow;
            saveOptions.Format = Aspose.Pdf.DocSaveOptions.DocFormat.DocX;

            doc.Save(outputFile, saveOptions);
        }

        return outputFile;
    }

    static void Convert(List<string> ValidFiles, string format)
    {

        var ThreadOptions = new ParallelOptions() { MaxDegreeOfParallelism = 1 };// errors occur when set to more than 1
        var outputFolder = System.IO.Path.GetTempPath();

        Parallel.ForEach(ValidFiles, ThreadOptions, (file) =>
        {

            string password = "";

            try
            {
                switch (format)
                {

                    case "msword":
                        var resultFile = convertPDFToWord(file, outputFolder, password);
                        break;
                        //case FORMAT_ENUM.POWERPOINT:
                        //    resultFile = convertPDFToPowerPoint(file, outputFolder, password);
                        //    break;
                        //case FORMAT_ENUM.MSEXCEL:
                        //    resultFile = convertPDFToExcel(file, outputFolder, password);
                        //    break;
                        //case FORMAT_ENUM.PNG:
                        //    resultFile = convertPDFToJpg(file, outputFolder, password);
                        //    break;
                        //case FORMAT_ENUM.EPUB:
                        //    resultFile = convertPDFToEpub(file, outputFolder, password, useZip);
                        //    break;
                        //case FORMAT_ENUM.TEXT:
                        //    resultFile = convertPDFToText(file, outputFolder, password);
                        //    break;
                }
            }
            catch (Exception fileEx)
            {
                throw fileEx;
            }

        });
        }

Around the Horn.pdf (337.8 KB)

#4

To reproduce the issue, make 100 copies of the attached PDF and pass them into the ValidFiles list. Set the MaxDegreeOfParallelism to 4.

#5

@amani7,

Thank you for contacting support.

Can you please share complete environment details and version details to further investigate this issue on our end.

#6

Running on Windows 10, Visual Studio 2017 and Aspose.PDF version 20.3.0.0. Application is running on .NET 4.6.1 targeting AnyCPU.

#7

@amani7,

Thanks for contacting support.

I have observed your issue and like to inform that I have created investigation ticket with ID PDFNET-48334 in our issue tracking system to investigate and resolve this issue as soon possible.