求C#高手帮我看看程序！！关于MIMI邮件解码的问题

   这里有人对MIME邮件解码比较了解的吗？可否帮我看看到底出了什么错呢？我的程序可以获取邮件，但是解码以后却什么都显示不出来！！过两天就要交大作业了，继续各路大侠的帮助！！                        //获取邮件内容
private void RetrieveBtn_Click(object sender, System.EventArgs e)
{
            Message.Clear();//清除邮件内容显示区          
            try
            {
                // 定义接收邮箱中的第几封邮件的命令
                Data = "RETR " + Number.Text + CRLF;
                szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
                NetStrm.Write(szData, 0, szData.Length); //向服务器发送接收邮件命令
                string szTemp;
                szTemp = RdStrm.ReadLine();             
           //解析接收的邮件内容 
                if (szTemp[0] != '-')     
                  {                 
                    while(szTemp!=".")
                    {                        Message.Text = Message.Text + "发送者：" + ParseSender(szTemp).ToString() + CRLF;
                        Message.Text = Message.Text + "接收者：" + ParseReciever(szTemp).ToString() + CRLF;
                        Message.Text = Message.Text + "主题：" + ParseSubject(szTemp).ToString() + CRLF;
                        Message.Text = Message.Text + "内容：" + ParseEmailText(szTemp).ToString() + CRLF;
                        szTemp = RdStrm.ReadLine();
                    }
                }
            }
catch(InvalidOperationException err)
{
Status.Items.Add("Error: "+err.ToString());
} }        //========================对发送者的信息进行解码=================================        public string ParseSender(string emailContent)
        {
            string pat = @"^From:\s*(?<sender>.*)\s*\r\n";
         
            Match m = Regex.Match(emailContent, pat, RegexOptions.IgnoreCase | RegexOptions.Multiline);
            string sender = m.Groups["sender"].ToString();
            pat = "\"?=\\?(?<TextEncoding>.+)\\?(?<encodingmethod>[A-Z])\\?(?<encodedText>.*)\\?=\"?(?<other>.*)$";
            m = Regex.Match(sender, pat, RegexOptions.IgnoreCase);
            string TextEncoding = m.Groups["TextEncoding"].ToString();
            string encodingmethod = m.Groups["encodingmethod"].ToString();
            string encodedText = m.Groups["encodedText"].ToString();
            string other = m.Groups["other"].ToString();          if (encodingmethod.ToUpper().Equals("B"))
            {
                byte[] inputBytes = Convert.FromBase64String(encodedText);
                string str = System.Text.Encoding.GetEncoding("utf-8").GetString(inputBytes, 0, inputBytes.Length);
                sender = str + other;
            }
            else if (encodingmethod.ToUpper().Equals("Q"))
            {                sender = ConvertFromQPString(encodedText, System.Text.Encoding.GetEncoding(TextEncoding)) + other;
            }            return sender;        }
        //对邮件主题进行解码
        public string ParseSubject(string emailContent)
        {            string pat = @"^Subject:\s*(?<Subject>.*)\n";
            Match m = Regex.Match(emailContent, pat, RegexOptions.IgnoreCase | RegexOptions.Multiline);
            string isubject = m.Groups["Subject"].ToString();
            pat = "\"?=\\?(?<TextEncoding>.+)\\?(?<encodingmethod>[A-Z])\\?(?<encodedText>.*)\\?=\"";
            m = Regex.Match(isubject, pat, RegexOptions.IgnoreCase);
            string TextEncoding = m.Groups["TextEncoding"].ToString();
            string encodingmethod = m.Groups["encodingmethod"].ToString();
            string encodedText = m.Groups["encodedText"].ToString();
            string other = m.Groups["other"].ToString();
            if (encodingmethod.ToUpper()=="B")
            {
                byte[] inputBytes = Convert.FromBase64String(encodedText);
                string str = System.Text.Encoding.GetEncoding("utf-8").GetString(inputBytes, 0, inputBytes.Length);
                isubject = str;
            }
            else if (encodingmethod.ToUpper().Equals("Q"))
            {                isubject = ConvertFromQPString(encodedText, System.Text.Encoding.GetEncoding(TextEncoding));
            }            return isubject;        }
        //对文件内容进行解码
        public string ParseEmailText(string emailContent)
        {
            string isTextOnly =@"^Content-Type:\s*multipart";
            bool t = Regex.IsMatch(emailContent,isTextOnly,RegexOptions.Multiline);
            if(t)
            {
                string pat = @"^(?<boundary>.*)\nContent-Type:\s*text/plain";
                Match match = Regex.Match(emailContent, pat, RegexOptions.Multiline);
                string boundary = match.Groups["boundary"].ToString();                pat = @"^Content-Type:\s*text/plain[\s\S]*?Content-Transfer-Encoding:\s*(?<encodingMethod>.*)\n(?<crytext>[\s\S]*?)"+boundary;                Match myMatches = Regex.Match(emailContent, pat, RegexOptions.IgnoreCase | RegexOptions.Multiline);                GroupCollection myGroup = myMatches.Groups;
                string crytext = myGroup["crytext"].ToString();//title变量存储From域的内容 
                string encodingMethod = myGroup["encodingMethod"].ToString();
                if (encodingMethod.ToUpper().Equals("BASE64"))
                {
                    crytext = crytext.Replace("\n", "");
                    byte[] inputBytes = Convert.FromBase64String(crytext);
                    string EmailText = System.Text.Encoding.GetEncoding("utf-8").GetString(inputBytes, 0, inputBytes.Length);
                    return EmailText;
                }
                else
                {
                    return ConvertFromQPString(crytext,System.Text.Encoding.GetEncoding(54936)).Replace("\n","\r\n");
                }
            }
            else
            {
                string pat = @"^Content-Type:\s*text/plain[\s\S]*?Content-Transfer-Encoding:\s*(?<encodingMethod>.*)\n(.*\n)*?\s*\n(?<crytext>[\s\S]+)";
                Match myMatches = Regex.Match(emailContent, pat, RegexOptions.IgnoreCase | RegexOptions.Multiline);                GroupCollection myGroup = myMatches.Groups;
                string crytext = myGroup["crytext"].ToString();//title变量存储From域的内容 
                string encodingMethod = myGroup["encodingMethod"].ToString();
                if (encodingMethod.ToUpper().Equals("BASE64"))
                {
                    crytext = crytext.Replace("\n", "");
                    byte[] inputBytes = Convert.FromBase64String(crytext);
                    string EmailText = System.Text.Encoding.GetEncoding("utf-8").GetString(inputBytes, 0, inputBytes.Length);
                    return EmailText;
                }
                else
                {
                    return ConvertFromQPString(crytext, System.Text.Encoding.GetEncoding("utf-8")).Replace("\n", "\r\n");
                }
            }
        }
        public string ConvertFromQPString(string quoted_printableString, System.Text.Encoding encoding)
        {
            string InputString = quoted_printableString;
            StringBuilder builder1 = new StringBuilder();
            // InputString = InputString.Replace("=\r\n", "");
            for (int num1 = 0; num1 < InputString.Length; num1++)
            {
                if (InputString[num1] == '=')
                {
                    try
                    {
                        if (HexToDec(InputString.Substring(num1 + 1, 2)) < 0x80)
                        {
                            if (HexToDec(InputString.Substring(num1 + 1, 2)) >= 0)
                            {
                                byte[] buffer1 = new byte[1] { (byte)HexToDec(InputString.Substring(num1 + 1, 2)) };
                                builder1.Append(encoding.GetString(buffer1, 0, buffer1.Length));
                                num1 += 2;
                            }
                        }
                        else if (InputString[num1 + 1] != '=')
                        {
                            byte[] buffer2 = new byte[2] { (byte)HexToDec(InputString.Substring(num1 + 1, 2)), (byte)HexToDec(InputString.Substring(num1 + 4, 2)) };
                            builder1.Append(encoding.GetString(buffer2, 0, buffer2.Length));
                            num1 += 5;
                        }
                    }
                    catch
                    {
                        builder1.Append(InputString.Substring(num1, 1));
                    }
                }
                else
                {
                    builder1.Append(InputString.Substring(num1, 1));
                }
            }
            return builder1.ToString();
        }
        private static int HexToDec(string hex)
        {
            int num1 = 0;
            string text1 = "0123456789ABCDEF";
            for (int num2 = 0; num2 < hex.Length; num2++)
            {
                if (text1.IndexOf(hex[num2]) == -1)
                {
                    return -1;
                }
                num1 = (num1 * 0x10) + text1.IndexOf(hex[num2]);
            }
            return num1;
        }
    }