gistfile1.txt

        public Batch CreateAttachmentBatch(CreateAttachmentBatchRequest request)
        {
            String requestTxtFileCSVContents = "Name,ParentId,Body" + Environment.NewLine;
            requestTxtFileCSVContents += request.FilePath + "," + request.ParentId + ",#" + request.FilePath;

            using (MemoryStream memoryStream = new MemoryStream())
            {
                using (var archive = new ZipArchive(memoryStream, ZipArchiveMode.Create, true))
                {
                    byte[] requestTxtFileCSVContentsBytes = UTF8Encoding.UTF8.GetBytes(requestTxtFileCSVContents);
                    var requestTxtFileInArchive = archive.CreateEntry("request.txt");
                    using (var entryStream = requestTxtFileInArchive.Open())
                    using (var fileToCompressStream = new MemoryStream(requestTxtFileCSVContentsBytes))
                    {
                        fileToCompressStream.CopyTo(entryStream);
                    }

                    byte[] attachmentFileContentsBytes = File.ReadAllBytes(request.FilePath);
                    var attachmentFileInArchive = archive.CreateEntry(request.FilePath);
                    using (var attachmentEntryStream = attachmentFileInArchive.Open())
                    using (var attachmentFileToCompressStream = new MemoryStream(attachmentFileContentsBytes))
                    {
                        attachmentFileToCompressStream.CopyTo(attachmentEntryStream);
                    }

                    byte[] zipFileBytes = memoryStream.ToArray();

                    String requestUrl = "https://" + _sfService.Pod + ".salesforce.com/services/async/31.0/job/" + request.JobId + "/batch";

                    byte[] responseBytes = invokeRestAPI(requestUrl, zipFileBytes, "POST", "zip/csv");

                    String resultXML = UTF8Encoding.UTF8.GetString(responseBytes);

                    return Batch.CreateBatch(resultXML);
                }
            }
        }