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[ASP.net教程]微软的坑,你有踩过吗?


  最近在做一个很简单的小工具,需求大概是这样的,做一个定时任务系统,定期从服务器上统计相关的业务数据,生成相关报表,然后以Excel方式发送给相关人员。任务很简单,定时任务没问题,生成报表没问题,导出Excel没问题,导出的Excel放在C盘temp目录下,然后设好发送时间,一切都感觉妥妥的,结果也很美好,过了10秒钟(本也测试,时间设得很短),邮件也妥妥的收到,附件中的excel表格也妥妥的能打开,报表也没问题。Oh,yeah,so,easy..,即然结果这么美好,那就打包发布吧。

  此处省略100字,就部署完了。

  嘀哒。。嘀哒。。,10秒,20秒,30秒,。。。没搞错,为了先报一个起来,我在正式环境也是设置了10秒运行一次呀?这10秒也太漫长了吧?1分钟了,好吧,应该是出问题了,心里仍在想着是不是哪部署出了问题呀,也不应该呀,就这么简单的一个小工具是吧?

  此处省略200字,检查部署没有任何问题。好吧,查日志。

  果不其然,报错了,错得还很趾高气扬:  

System.FormatException: An invalid character was found in the mail header: '周'.
at System.Net.Mime.MailBnfHelper.GetTokenOrQuotedString(String data, StringBuilder builder)
at System.Net.Mime.ContentDisposition.ToString()
at System.Net.Mime.ContentDisposition.PersistIfNeeded(HeaderCollection headers, Boolean forcePersist)
at System.Net.Mime.MimePart.Send(BaseWriter writer)
at System.Net.Mime.MimeMultiPart.Send(BaseWriter writer)
at System.Net.Mail.SmtpClient.Send(MailMessage message)
--- End of inner exception stack trace ---
at System.Net.Mail.SmtpClient.Send(MailMessage message)

  没搞错,An invalid character was found in the mail header“周”? 这应该是乱码时,才会这样提示的吧?页面我邮件发送直接是使用SmtpClient,根本就没有设置header呀?

  此处省略1000字,各种度娘,各种google,各种恶补邮件头,MIME的知识,各种设置附件ContentType。结果都一样,唯一不一样的就是乱码的字,从“周“变成不是”周“。。

  此处省略2000字,突然听同事说有可能和CurrentCulture有关系,顿时眼前一亮,赶紧google一下,果然,有答案了。

  .net 4.0中有一个Bug:Culture Bug in ContentDisposition,即只要设置了ContentDisposition的时间,任何时间,如CreationDate,或是ModificationDate,.net内部,会将这些时间通过调用DateTime的toString方法传递给SmtpDateTime,问题就出现在,这些时间格式是和本地语言环境相关的,toString很可能出问题。(官方说法是在vs2013中修复了这个问题)好了,找到问题就好办了,即然和Culture有关,我又不想升级.net Framework,那就让它和CurrentCulture暂时没关系吧。

 1 var currentCulture = Thread.CurrentThread.CurrentCulture; 2       var attachment = new Attachment(attachmentFile, displayName); 3       try 4       { 5         ... 6         Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;        7         attachment.ContentDisposition.CreationDate = File.GetCreationTime(attachmentFilePath); 8         attachment.ContentDisposition.ModificationDate = File.GetLastWriteTime(attachmentFilePath); 9         attachment.ContentDisposition.ReadDate = File.GetLastAccessTime(attachmentFilePath);10         ...11       }12       finally13       {14         Thread.CurrentThread.CurrentCulture = currentCulture;15       }

  果然,那个另人讨厌的”周“不见了,10秒后邮件到了,哈哈,,终于可以收工了。等等。。,为什么我一个好好的Excel附件,发出来后,即没文件名(实际应该有,只是乱码了,没显示出来),里面的内容也是乱码的?天呀,你在和我开玩笑嘛?我本地开发环境都是好好的呀!!

  此处省略3000字,各种尝试,各种用网友的办法,各种失去理智的尝试,各种。。无果而终。

  就快要放弃的时间,突然想起,有问题找stackoverflow.com呀,度啥娘呀。好吧,我是乱了方寸了。谁让我本应该2小时前就下班的,到现在问题还没头绪呢。果然,这个问题早在n年前就有人发现了,仍然是我们可爱的微软埋下的坑:

  

  (机器翻译,将就着看哈)。

  好吧,我败了。只能怪我爱得太深了,竟不曾怀疑过你。

  可我还是不想升级Framework,生产环境,可不是闹着玩的呢。 

  试着用网友ZYD的方法,把文件名先编码拆分,问题可以得到解决:

  

 1 ... 2     Attachment attachment = null; 3       //添加附件 4       if (!String.IsNullOrEmpty(attachmentFilePath) && File.Exists(attachmentFilePath)) 5       { 6         attachment = CreateAttachment(WriteFileToMemory(attachmentFilePath), attachmentFileName,contentType,attachmentFilePath); 7         message.Attachments.Add(attachment); 8  9       }10     ...11     12     public static Attachment CreateAttachment(Stream attachmentFile, string displayName, string contentType, string attachmentFilePath)13     {14       var currentCulture = Thread.CurrentThread.CurrentCulture;//.net4.0 bug,15       var attachment = new Attachment(attachmentFile, displayName);16       try17       {18         Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;19         attachment.ContentType = new ContentType(contentType);20         attachment.ContentDisposition.CreationDate = File.GetCreationTime(attachmentFilePath);21         attachment.ContentDisposition.ModificationDate = File.GetLastWriteTime(attachmentFilePath);22         attachment.ContentDisposition.ReadDate = File.GetLastAccessTime(attachmentFilePath);23         attachment.TransferEncoding = TransferEncoding.Base64;24         attachment.NameEncoding = Encoding.UTF8;25         string encodedAttachmentName = Convert.ToBase64String(Encoding.UTF8.GetBytes(displayName));26         encodedAttachmentName = SplitEncodedAttachmentName(encodedAttachmentName);27         attachment.Name = encodedAttachmentName;28       }29       finally30       {31         Thread.CurrentThread.CurrentCulture = currentCulture;32       }33       return attachment;34     }35     36     private static Stream WriteFileToMemory(string filePath)37     {38       var fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);39       return fileStream;40     }    41 42     private static string SplitEncodedAttachmentName(string encoded)43     {44       const string encodingtoken = "=?UTF-8?B?";45       const string softbreak = "?=";46       const int maxChunkLength = 30;47       int splitLength = maxChunkLength - encodingtoken.Length - (softbreak.Length * 2);48       IEnumerable<string> parts = SplitByLength(encoded, splitLength);49       string encodedAttachmentName = encodingtoken;50       foreach (var part in parts)51       {52         encodedAttachmentName += part + softbreak + encodingtoken;53       }54       encodedAttachmentName = encodedAttachmentName.Remove(encodedAttachmentName.Length - encodingtoken.Length, encodingtoken.Length);55       return encodedAttachmentName;56     }57 58     private static IEnumerable<string> SplitByLength(string stringToSplit, int length)59     {60       while (stringToSplit.Length > length)61       {62         yield return stringToSplit.Substring(0, length);63         stringToSplit = stringToSplit.Substring(length);64       }65       if (stringToSplit.Length > 0)66       {67         yield return stringToSplit;68       }69     }

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  过程是坎坷的,结局是美好的!

  只能怪我爱得太深了,竟不曾怀疑过你。用它来结语,再好不过了吧!