MailMessage to EML

EML格式是微软公司在Outlook中所使用的一种遵循RFC822及其后续扩展的文件格式,并成为各类电子邮件软件的通用格式。

做个笔记，C# 邮件处理保存为eml格式；

一、网上好多这样的写法，可以在.net formwork4.5里面百试不爽…………

  /// <summary>
        /// 2.0可以允许  4.5不可以
        /// </summary>
        /// <param name="msg"></param>
        /// <returns></returns>
        public static byte[] MailMessageToArray(MailMessage msg)
        {
            const BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.FlattenHierarchy;
            using (var ms = new MemoryStream())
            {
                var assembly = typeof(SmtpClient).Assembly;
                var writerType = assembly.GetType("System.Net.Mail.MailWriter");
                var writer = Activator.CreateInstance(writerType, flags, null, new object[] { ms }, CultureInfo.InvariantCulture);
                msg.GetType().GetMethod("Send", flags).Invoke(msg, new[] { writer, true });
                return ms.ToArray();
            }
        }

.netformwork 4.5 运行报错---“用户代码未处理TargetParameterCountException 参数不匹配”

二、柳暗花明

不得不说还是老外的技术牛逼些……

      /// <summary>
        /// MailMessage 转换成eml
        /// </summary>
        /// <param name="msg">MailMessage</param>
        /// <returns>eml字符串</returns> 
        static string MailMessageToEml(MailMessage msg)
        {
            Assembly assembly = typeof(SmtpClient).Assembly;
            Type mailWriterType = assembly.GetType("System.Net.Mail.MailWriter");
            using (MemoryStream stream = new MemoryStream())
            {
                ConstructorInfo mailWriterContructor = mailWriterType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { typeof(Stream) }, null);
                object mailWriter = mailWriterContructor.Invoke(new object[] { stream });
                MethodInfo sendMethod = typeof(MailMessage).GetMethod("Send", BindingFlags.Instance | BindingFlags.NonPublic);
                sendMethod.Invoke(msg, BindingFlags.Instance | BindingFlags.NonPublic, null, new[] { mailWriter, true, true }, null); 
                return System.Text.Encoding.UTF8.GetString(stream.ToArray());
                //return Encoding.Default.GetString( stream.ToArray());
            } 
        }

效果杠杆的

国外的大牛就是一样，发现和他的差距太TM的不小。。。。还有一种解决方案

public static class MailMessageExtensions
{
    public static string RawMessage(this MailMessage m)
    {
        var smtpClient = new SmtpClient { DeliveryMethod = SmtpDeliveryMethod.SpecifiedPickupDirectory };

        using (var tempDir = new TemporaryDirectory())
        {
            smtpClient.PickupDirectoryLocation = tempDir.DirectoryPath;
            smtpClient.Send(m);
            var emlFile = Directory.GetFiles(smtpClient.PickupDirectoryLocation).FirstOrDefault();
            if (emlFile != null)
            {
                return File.ReadAllText(emlFile);
            }
            else
                return null;
        }
        return null;
    }

}

class TemporaryDirectory : IDisposable
{
    public TemporaryDirectory()
    {
        DirectoryPath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
        Directory.CreateDirectory(DirectoryPath);
    }

    public string DirectoryPath { get; private set; }

    public void Dispose()
    {
        if (Directory.Exists(DirectoryPath))
            Directory.Delete(DirectoryPath, true);
    }
}

调用方法

        public void Mime(string mailFrom, string subject, string body, string mailTo)
        { 
            MailMessage message = new MailMessage();
            message.From = new MailAddress(mailFrom, "", Encoding.UTF8);
            message.To.Add(new MailAddress(mailTo));
            message.Subject = subject;
            message.SubjectEncoding = Encoding.UTF8;////主题编码
            message.Body = body;// "<html><body><h1>Welcome</h1><br>This is an HTML message for outofmemory.cn.</body></html>";
            message.IsBodyHtml = true;
            message.BodyEncoding = Encoding.UTF8;//邮件内容编码
            message.Priority = MailPriority.High;//优先级
             
            //string str=MailMessageToEml(message);
            string ems = MailMessageExtensions.RawMessage(message);
        }

结果然是令人兴奋，对比而言选择方案一，至于为什么……看看代码就晓得了！