Question

我正在尝试压缩XML树并将其用作电子邮件附件。发送带附件的电子邮件成功，但创建的zip文件总是损坏 - 它不是有效的zip文件，但包含二进制数据。

问题重新创建如下，具体见BuildAttachment()：

static void Main(string[] args)
{
    try
    {
        var report = new XElement("Report",
            new XElement("Product",
                new XElement("ID", "10000001"),
                new XElement("Name", "abcdefghijklm"),
                new XElement("Group", "nopqrstuvwxyz")
            )
        );
        var mailMessage = BuildMessage(report);
        EmailMessage(mailMessage);
        Thread.Sleep(10000);
    }
    catch (Exception e) { Console.WriteLine(e.Message); }
}
static MailMessage BuildMessage(XElement report)
{
    string from = "email1@address.com";
    string to = "email2@address.com";
    var message = new MailMessage(from, to, "Subject text", "Body text");

    var attachment = BuildAttachment(report);
    message.Attachments.Add(attachment);

    return message;
}
static Attachment BuildAttachment(XElement report)
{
    var inStream = new MemoryStream();
    report.Save(inStream);
    inStream.Position = 0;

    var outStream = new MemoryStream();
    var compress = new DeflateStream(outStream, CompressionMode.Compress);
    inStream.CopyTo(compress);

    outStream.Position = 0;
    return new Attachment(outStream, "report.zip", "application/zip");
}
static void EmailMessage(MailMessage message)
{
    var smtpClient = new SmtpClient("127.0.0.1");
    smtpClient.SendCompleted += SendCompletedCallback;
    smtpClient.SendAsync(message, null);
}
static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
{
    if (e.Error != null)
        Console.WriteLine(e.Error.ToString());
}

将问题放在上下文中：它是Windows服务应用程序的一部分，所以我不想在磁盘上创建文件，并且电子邮件消息还包含xslt转换的xml树的备用视图，所以我不想要完全不同的解决方案。

有关zip文件损坏的任何建议吗？

Answer 1

我知道这是一个古老的问题，但在我搜索时却出现了。

以下是我使用System.IO.Compression.ZipArchive (requires .NET 4.5 or higher)添加压缩（zip）附件的解决方案[基于acraig5075的答案]：

byte[] report = GetSomeReportAsByteArray();
string fileName = "file.txt";

using (MemoryStream memoryStream = new MemoryStream())
{
    using (ZipArchive zipArchive = new ZipArchive(memoryStream, ZipArchiveMode.Update))
    {
        ZipArchiveEntry zipArchiveEntry = zipArchive.CreateEntry(fileName);
        using (StreamWriter streamWriter = new StreamWriter(zipArchiveEntry.Open()))
        {
            streamWriter.Write(Encoding.Default.GetString(report));
        }
    }

    MemoryStream attachmentStream = new MemoryStream(memoryStream.ToArray());

    Attachment attachment = new Attachment(attachmentStream, fileName + ".zip", MediaTypeNames.Application.Zip);
    mail.Attachments.Add(attachment);
}

Answer 2

您没有创建有效的zip文件，只是创建压缩流并将其写入扩展名为*.zip的文件。您应该使用.NET zip库而不是DeflateStream。

您可以使用DotNetZip Library：

之类的内容

DotNetZip是一个易于使用，快速，免费的类库和工具集操纵zip文件或文件夹。 Zip和Unzip很简单：有 DotNetZip，用VB编写的.NET应用程序，C＃ - 任何.NET语言 - 可以轻松创建，读取，提取或更新zip文件。对于Mono或MS .NET。

如果您有约束但无法使用外部库，则可以尝试使用GZipStream并添加扩展名为*.gz的附件，这将受到常用压缩工具的支持。

作为将来参考的有用信息，.NET 4.5将最终通过ZipArchive类引入对zip存档的本机支持。

Answer 3

为了将来参考，在接受的答案中建议的替代GZipStream方法，通过如下更改上述代码来生成.gz存档。

static Attachment BuildAttachment(XElement report)
{
    var inStream = new MemoryStream();
    report.Save(inStream);
    inStream.Position = 0;

    var outStream = new MemoryStream();
    using (var compress = new GZipStream(outStream, CompressionMode.Compress))
    {
        inStream.CopyTo(compress);
        compress.Close();
    }

    var ms = new MemoryStream(outStream.ToArray());
    Attachment attachment = new Attachment(ms, "report.xml.gz", "application/gzip");
    return attachment;
}

需要using阻止和ToArray()通话。

Answer 4

感谢＆＃34; Neils。回答，我创建了一个静态C＃函数来管理附件，如果大于1Mb，则将其压缩。希望这对任何人都有帮助。

public static Attachment CreateAttachment(string fileNameAndPath, bool zipIfTooLarge = true, int bytes = 1 << 20)
{
    if (!zipIfTooLarge)
    {
        return new Attachment(fileNameAndPath);
    }

    var fileInfo = new FileInfo(fileNameAndPath);
    // Less than 1Mb just attach as is.
    if (fileInfo.Length < bytes)
    {
        var attachment = new Attachment(fileNameAndPath);

        return attachment;
    }

    byte[] fileBytes = File.ReadAllBytes(fileNameAndPath);

    using (var memoryStream = new MemoryStream())
    {
        string fileName = Path.GetFileName(fileNameAndPath);

        using (var zipArchive = new ZipArchive(memoryStream, ZipArchiveMode.Create))
        {
            ZipArchiveEntry zipArchiveEntry = zipArchive.CreateEntry(fileName, CompressionLevel.Optimal);

            using (var streamWriter = new StreamWriter(zipArchiveEntry.Open()))
            {
                streamWriter.Write(Encoding.Default.GetString(fileBytes));
            }
        }

        var attachmentStream = new MemoryStream(memoryStream.ToArray());
        string zipname = $"{Path.GetFileNameWithoutExtension(fileName)}.zip";
        var attachment = new Attachment(attachmentStream, zipname, MediaTypeNames.Application.Zip);

        return attachment;
    }
}

压缩MemoryStream以获取电子邮件附件

4 个答案: