c# - PdfDocument 在关闭后保持锁定状态

Question

我有一个 Windows 服务，可以即时合并 PDF，然后将它们移动到另一个位置。在大多数情况下，我无法控制某人想要合并的内容。碰巧经常会处理损坏的 PDF，因此创建新的 PdfDocument 会抛出 PdfException“未找到预告片”。我正在捕获异常并关闭文档，但它在关闭后出现 PDF 本身仍然以某种方式被锁定。我需要删除该目录，但在尝试这样做时它会抛出 IOException 并使服务崩溃。

我已经验证调用 PdfDocument 构造函数是锁定 pdf 的原因，并且在关闭文件后立即保持锁定状态。

有什么想法吗？ iText 可以做些什么来帮助解决这个问题，还是我需要想出一些办法来预先检查损坏的 PDF？

进程目录

---

    private void ProcessDirectory(string directoryPath)
    {
        EventLogManager.WriteInformation("ProcessDirectory");
        // DON'T TOUCH THE BACKUPS, ERRORS AND WORK DIRECTORIES.  Just in case they were made or renamed after the fact for some reason
        if (directoryPath != this._errorsPath && directoryPath != this._backupsPath && directoryPath != this._workPath)
        {
            string pdfJsonPath = System.IO.Path.Combine(directoryPath, "pdf.json");

            if (File.Exists(pdfJsonPath))
            {
                string workPath = System.IO.Path.Combine(this._workPath, System.IO.Path.GetFileName(directoryPath));

                try
                {
                    CopyToDirectory(directoryPath, workPath);

                    PdfMerge pdfMerge = null;

                    string jsonPath = System.IO.Path.Combine(workPath, "pdf.json");
                    using (StreamReader r = Helpers.GetStreamReader(jsonPath))
                    {
                        string json = r.ReadToEnd();
                        pdfMerge = JsonConvert.DeserializeObject<PdfMerge>(json);
                    }

                    FillFormFields(workPath, pdfMerge);

                    if (pdfMerge.Pdfs.Any(p => !String.IsNullOrWhiteSpace(p.OverlayFilename)))
                    {
                        ApplyOverlays(workPath, pdfMerge);
                    }

                    MergePdfs(workPath, pdfMerge);
                    //NumberPages(workPath, pdfMerge);
                    FinishPdf(workPath, pdfMerge);

                    // Move original to backups directory
                    if (DoSaveBackups)
                    {
                        string backupsPath = System.IO.Path.Combine(this._backupsPath, String.Format("{0}_{1}", System.IO.Path.GetFileName(directoryPath), DateTime.Now.ToString("yyyyMMddHHmmss")));
                        Directory.Move(directoryPath, backupsPath);
                    }
                    else
                    {
                        Directory.Delete(directoryPath, true);
                    }
                }
                catch (Exception ex)
                {
                    EventLogManager.WriteError(ex);

                    if (DoSaveErrors)
                    {
                        // Move original to errors directory
                        string errorsPath = System.IO.Path.Combine(this._errorsPath, String.Format("{0}_{1}", System.IO.Path.GetFileName(directoryPath), DateTime.Now.ToString("yyyyMMddHHmmss")));
                        Directory.Move(directoryPath, errorsPath);
                    }
                    else
                    {
                        Directory.Delete(directoryPath, true);
                    }
                }

                // Delete work directory
                // THIS IS WHERE THE IOEXCEPTION OCCURS AND THE SERVICE CRASHES
                Directory.Delete(workPath, true);
            }
            else
            {
                EventLogManager.WriteInformation(String.Format("No pdf.json file.  {0} skipped.", directoryPath));
            }
        }
    }

填充表单字段

---

    private void FillFormFields(string directoryPath, PdfMerge pdfMerge)
    {
        if (pdfMerge != null && pdfMerge.Pdfs != null)
        {
            string formPath = String.Empty;
            string newFilePath;
            PdfDocument document = null;
            PdfAcroForm form;
            PdfFormField pdfFormField;

            foreach (var pdf in pdfMerge.Pdfs)
            {
                try
                {
                    formPath = System.IO.Path.Combine(directoryPath, pdf.Filename);
                    newFilePath = System.IO.Path.Combine(
                        directoryPath,
                        String.Format("{0}{1}", String.Format("{0}{1}", System.IO.Path.GetFileNameWithoutExtension(pdf.Filename), "_Revised"), System.IO.Path.GetExtension(pdf.Filename)));

                    // THIS IS WHERE THE PDFEXCEPTOIN OCCURS
                    document = new PdfDocument(Helpers.GetPdfReader(formPath), new PdfWriter(newFilePath));
                    form = PdfAcroForm.GetAcroForm(document, true);

                    if (pdf.Fields != null && pdf.Fields.Count > 0)
                    {
                        foreach (var field in pdf.Fields)
                        {
                            if (field.Value != null)
                            {
                                pdfFormField = form.GetField(field.Name);

                                if (pdfFormField != null)
                                {
                                    form.GetField(field.Name).SetValue(field.Value);
                                }
                                else
                                {
                                    EventLogManager.WriteWarning(String.Format("Field '{0}' does not exist in '{1}'", field.Name, pdf.Filename));
                                }
                            }
                        }
                    }

                    form.FlattenFields();
                }
                catch (Exception ex)
                {
                    throw new Exception(String.Format("An exception occurred filling form fields for {0}", pdf.Filename), ex);
                }
                finally
                {
                    if (document != null)
                    {
                        document.Close();
                    }
                }

                // Now rename the new one back to the old name
                File.Delete(formPath);
                File.Move(newFilePath, formPath);
            }
        }
    }

更新

似乎为了正确处理所有内容，您必须将单独的 PdfReader 和 PdfWriter 对象声明为 using 语句并将它们传递到 PdfDocument。像这样:

    using (reader = Helpers.GetPdfReader(formPath))
    {
        using (writer = new PdfWriter(newFilePath))
        {
            using (document = new PdfDocument(reader, writer))
            {
                // The rest of the code here
            }
        }
    }

我不确定为什么除了 iText 在处理 PdfDocument 时没有处理单独的 PdfReader 和 PdfWriter 之外，我认为它会处理。

Answer 1

找出哪些 itext7 类实现了 IDisposable(从文档或 Visual Studio 对象浏览器等)，并确保在 using block 中使用它们，就像您已经为 StreamReader 使用 block 一样。

编辑:@sourkrause 的解决方案可以缩短为:

using (reader = Helpers.GetPdfReader(formPath))
using (writer = new PdfWriter(newFilePath))
using (document = new PdfDocument(reader, writer))
{
    // The rest of the code here
}