c# - 使用 GZIP 流和内存流正确压缩 CSV

Question

我正在使用 GZIPStream 和 MemoryStream 压缩 CSV 文件，并注意到结果文件有些奇怪。 CSV 似乎没有被正确识别。当文件附加到电子邮件时显示，但保存在 Windows 桌面上时工作正常。

这是处理 gzip 部分的当前片段:

GZipStream gStream = null;
        MemoryStream mStream = null;
        MemoryStream mStream2 = null;
        try
        {
            if (attachment.Length > 0)
            {                    
                mStream = new MemoryStream();

                gStream = new GZipStream(mStream, CompressionMode.Compress);                    
                byte[] bytes = System.Text.Encoding.UTF8.GetBytes(attachment.ToString());
                gStream.Write(bytes, 0, bytes.Length);
                gStream.Close();

                mStream2 = new MemoryStream(mStream.ToArray());
                Attachment emailAttachement = new Attachment(mStream2, "myGzip.csv.gz", "application/x-Gzip");                                         
                mailMessage.Attachments.Add(emailAttachement);
            }

        }

Answer 1

我能够使用下面的代码进行 gzip 压缩并发送 csv。 GZipStream 在其 Close() 方法被调用之前不会完成写入。当创建 gzipStream 的 using block 完成时会发生这种情况。即使使用 block 完成后流输出也关闭，仍然可以使用 ToArray() 或 GetBuffer() 方法从输出流中检索数据。请看这个blog entry获取更多信息。

public void SendEmailWithGZippedAttachment(string fromAddress, string toAddress, string subject, string body, string attachmentText)
{
        const string filename = "myfile.csv.gz";
        var message = new MailMessage(fromAddress, toAddress, subject, body);

        //Compress and save buffer
        var output = new MemoryStream();
        using (var gzipStream = new GZipStream(output, CompressionMode.Compress))
        {
            using(var input = new MemoryStream(Encoding.UTF8.GetBytes(attachmentText)))
            {
                input.CopyTo(gzipStream);
            }
        }
        //output.ToArray is still accessible even though output is closed
        byte[] buffer = output.ToArray(); 

        //Attach and send email
        using(var stream = new MemoryStream(buffer))
        {
            message.Attachments.Add(new Attachment(stream, filename, "application/x-gzip"));
            var smtp = new SmtpClient("mail.myemailserver.com") {Credentials = new NetworkCredential("username", "password")};
            smtp.Send(message);
        }
}