C＃電子郵件主題解析

Question

我正在構建一個用C＃讀取電子郵件的系統。我解析這個主題時遇到了一個問題，我認爲這個問題與編碼有關。

我正在閱讀的主題如下：=?ISO-8859-1?Q?=E6=F8sd=E5f=F8sdf_sdfsdf?=，發送的原始主題是æøsdåføsdf sdfsdf（挪威語中的人物）。

任何想法如何改變編碼或解析正確？到目前爲止，我試圖使用C＃編碼轉換技術將主題編碼爲utf8，但沒有任何運氣。

這裏是我試過的解決方案之一：

Encoding iso = Encoding.GetEncoding("iso-8859-1"); 
Encoding utf = Encoding.UTF8; 
string decodedSubject = 
    utf.GetString(Encoding.Convert(utf, iso, 
            iso.GetBytes(m.Subject.Split('?')[3]))); 

Answer 1

編碼被稱爲quoted printable。

查看this的問題的答案。

從接受answer改編：

public string DecodeQuotedPrintable(string value) 
{ 
     Attachment attachment = Attachment.CreateAttachmentFromString("", value); 
     return attachment.Name; 
} 

當傳遞的字符串=?ISO-8859-1?Q?=E6=F8sd=E5f=F8sdf_sdfsdf?=這將返回 「æøsdåføsdf_sdfsdf」。

Answer 2

public static string DecodeEncodedWordValue(string mimeString) 
    { 
     var regex = new Regex(@"=\?(?<charset>.*?)\?(?<encoding>[qQbB])\?(?<value>.*?)\?="); 
     var encodedString = mimeString; 
     var decodedString = string.Empty; 

     while (encodedString.Length > 0) 
     { 
      var match = regex.Match(encodedString); 
      if (match.Success) 
      { 
       // If the match isn't at the start of the string, copy the initial few chars to the output 
       decodedString += encodedString.Substring(0, match.Index); 

       var charset = match.Groups["charset"].Value; 
       var encoding = match.Groups["encoding"].Value.ToUpper(); 
       var value = match.Groups["value"].Value; 

       if (encoding.Equals("B")) 
       { 
        // Encoded value is Base-64 
        var bytes = Convert.FromBase64String(value); 
        decodedString += Encoding.GetEncoding(charset).GetString(bytes); 
       } 
       else if (encoding.Equals("Q")) 
       { 
        // Encoded value is Quoted-Printable 
        // Parse looking for =XX where XX is hexadecimal 
        var regx = new Regex("(\\=([0-9A-F][0-9A-F]))", RegexOptions.IgnoreCase); 
        decodedString += regx.Replace(value, new MatchEvaluator(delegate(Match m) 
        { 
         var hex = m.Groups[2].Value; 
         var iHex = Convert.ToInt32(hex, 16); 

         // Return the string in the charset defined 
         var bytes = new byte[1]; 
         bytes[0] = Convert.ToByte(iHex); 
         return Encoding.GetEncoding(charset).GetString(bytes); 
        })); 
        decodedString = decodedString.Replace('_', ' '); 
       } 
       else 
       { 
        // Encoded value not known, return original string 
        // (Match should not be successful in this case, so this code may never get hit) 
        decodedString += encodedString; 
        break; 
       } 

       // Trim off up to and including the match, then we'll loop and try matching again. 
       encodedString = encodedString.Substring(match.Index + match.Length); 
      } 
      else 
      { 
       // No match, not encoded, return original string 
       decodedString += encodedString; 
       break; 
      } 
     } 
     return decodedString; 
    }