我需要将多个文件流附加到同一个 pdf 文件

Question

我有一个函数可以将ZPL(斑马标签) 转换为 PDF 格式并保存文件。我想要做的不是每次都覆盖文件，而是想将文件流附加到文件（如果存在），写入新的（如果不存在）。

我尝试使用 filemode.append 设置一个新的文件流，但这似乎没有什么不同。

private static void SaveLabel(string label, string labelDir, string caseNumber)
    {
        var zpl = Encoding.UTF8.GetBytes(label);
        var fileName = $@"{labelDir}\{caseNumber}.pdf";

        // adjust print density (8dpm), label width (4 inches), label height (6 inches), and label index (0) as necessary
        var request = (HttpWebRequest)WebRequest.Create("http://api.labelary.com/v1/printers/8dpmm/labels/4x6/0/");
        request.Method = "POST";
        request.Accept = "application/pdf"; // omit this line to get PNG images back
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = zpl.Length;

        var requestStream = request.GetRequestStream();
        requestStream.Write(zpl, 0, zpl.Length);
        requestStream.Close();

        try
        {
            var response = (HttpWebResponse)request.GetResponse();
            var responseStream = response.GetResponseStream();
            if (!File.Exists(fileName))
                File.Create(fileName);

            using (var fileStream = File.Open(fileName, FileMode.Append))
            {
                responseStream?.CopyTo(fileStream);
                responseStream?.Close();
                fileStream.Close();
            }
        }
        catch (WebException e)
        {
            Console.WriteLine(@"Error: {0}", e.Status);
        }
    }

Answer 1

我首先检查文件是否存在（这意味着货件将有多个标签）。如果没有，则正常处理。如果是，则将该文件读入新的 pdf 文件。然后将当前响应流的内容读入第二个新的 pdf 文件。

然后我删除目标文件以释放新组合 pdf 的名称。然后我使用建议的 PDFSharp 链接并合并页面并保存为原始文件名。无论生成多少包装标签，这都将启用文件的连续附加。

private static void SaveLabel(string label, string labelDir, string caseNumber)
    {
        var zpl = Encoding.UTF8.GetBytes(label);
        var destFileName = $@"{labelDir}\{caseNumber}.pdf";

        // adjust print density (8dpm), label width (4 inches), label height (6 inches), and label index (0) as necessary
        var request = (HttpWebRequest)WebRequest.Create("http://api.labelary.com/v1/printers/8dpmm/labels/4x6/0/");
        request.Method = "POST";
        request.Accept = "application/pdf"; // omit this line to get PNG images back
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = zpl.Length;

        var requestStream = request.GetRequestStream();
        requestStream.Write(zpl, 0, zpl.Length);
        requestStream.Close();

        try
        {
            var response = (HttpWebResponse)request.GetResponse();
            var responseStream = response.GetResponseStream();

            if (File.Exists(destFileName))
            {
                var oldStream = File.OpenRead(destFileName);
                var oldFileName = $@"{labelDir}\{caseNumber}-1.pdf";
                using (var fileStream = File.Open(oldFileName, FileMode.Create))
                {
                    oldStream.CopyTo(fileStream);
                    oldStream.Close();
                    fileStream.Close();
                }

                var newFileName = $@"{labelDir}\{caseNumber}-2.pdf";
                using (var fileStream = File.Open(newFileName, FileMode.Create))
                {
                    responseStream?.CopyTo(fileStream);
                    responseStream?.Close();
                    fileStream.Close();
                }

                File.Delete(destFileName);

                using (var pdfOne = PdfReader.Open(oldFileName, PdfDocumentOpenMode.Import))
                {
                    using (var pdfTwo = PdfReader.Open(newFileName, PdfDocumentOpenMode.Import))
                    {
                        using (var outPdf = new PdfDocument())
                        {
                            CopyPages(pdfOne, outPdf);
                            CopyPages(pdfTwo, outPdf);

                            outPdf.Save(destFileName);
                        }
                    }
                }

                File.Delete(oldFileName);
                File.Delete(newFileName);
            }
            else
            {
                using (var fileStream = File.Open(destFileName, FileMode.Create))
                {
                    responseStream?.CopyTo(fileStream);
                    responseStream?.Close();
                    fileStream.Close();
                }
            }
        }
        catch (WebException e)
        {
            Console.WriteLine(@"Error: {0}", e.Status);
        }
    }