/// <summary>  /// 用于取得一個文本文件的編碼方式(Encoding)。  /// </summary>  public class TxtFileEncoder {  public TxtFileEncoder()  {   //    // TODO: 在此處添加構造函數邏輯    //   }  /// <summary>   /// 取得一個文本文件的編碼方式。如果無法在文件頭部找到有效的前導符，Encoding.Default將被返回。   /// </summary>   /// <param name="fileName">文件名。</param>   /// <returns></returns>   public static Encoding GetEncoding(string fileName)  {   return GetEncoding(fileName, Encoding.Default);  }  /// <summary>   /// 取得一個文本文件流的編碼方式。   /// </summary>   /// <param name="stream">文本文件流。</param>   /// <returns></returns>   public static Encoding GetEncoding(FileStream stream)  {   return GetEncoding(stream, Encoding.Default);  }  /// <summary>   /// 取得一個文本文件的編碼方式。   /// </summary>   /// <param name="fileName">文件名。</param>   /// <param name="defaultEncoding">默認編碼方式。當該方法無法從文件的頭部取得有效的前導符時，將返回該編碼方式。</param>   /// <returns></returns>   public static Encoding GetEncoding(string fileName, Encoding defaultEncoding)  {   FileStream fs = new FileStream(fileName, FileMode.Open);   Encoding targetEncoding = GetEncoding(fs, defaultEncoding);   fs.Close();   return targetEncoding;  }  /// <summary>   /// 取得一個文本文件流的編碼方式。   /// </summary>   /// <param name="stream">文本文件流。</param>   /// <param name="defaultEncoding">默認編碼方式。當該方法無法從文件的頭部取得有效的前導符時，將返回該編碼方式。</param>   /// <returns></returns>   public static Encoding GetEncoding(FileStream stream, Encoding defaultEncoding)  {   Encoding targetEncoding = defaultEncoding;   if (stream != null && stream.Length >= 2)   {    //保存文件流的前4個字節     byte byte1 = 0;    byte byte2 = 0;    byte byte3 = 0;    byte byte4 = 0;    //保存當前Seek位置     long origPos = stream.Seek(0, SeekOrigin.Begin);    stream.Seek(0, SeekOrigin.Begin);    int nByte = stream.ReadByte();    byte1 = Convert.ToByte(nByte);    byte2 = Convert.ToByte(stream.ReadByte());    if (stream.Length >= 3)    {     byte3 = Convert.ToByte(stream.ReadByte());    }    if (stream.Length >= 4)    {     byte4 = Convert.ToByte(stream.ReadByte());    }    //根據文件流的前4個字節判斷Encoding     //Unicode {0xFF, 0xFE};     //BE-Unicode {0xFE, 0xFF};     //UTF8 = {0xEF, 0xBB, 0xBF};     if (byte1 == 0xFE && byte2 == 0xFF)//UnicodeBe     {     targetEncoding = Encoding.BigEndianUnicode;    }    if (byte1 == 0xFF && byte2 == 0xFE && byte3 != 0xFF)//Unicode     {     targetEncoding = Encoding.Unicode;    }    if (byte1 == 0xEF && byte2 == 0xBB && byte3 == 0xBF)//UTF8     {     targetEncoding = Encoding.UTF8;    }    //恢復Seek位置       stream.Seek(origPos, SeekOrigin.Begin);   }   return targetEncoding;  }  // 新增加一個方法，解決了不帶BOM的 UTF8 編碼問題   /// <summary>   /// 通過給定的文件流，判斷文件的編碼類型   /// </summary>   /// <param name="fs">文件流</param>   /// <returns>文件的編碼類型</returns>   public static System.Text.Encoding GetEncoding(Stream fs)  {   byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };   byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };   byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //帶BOM    Encoding reVal = Encoding.Default;   BinaryReader r = new BinaryReader(fs, System.Text.Encoding.Default);   byte[] ss = r.ReadBytes(4);   if (ss[0] == 0xFE && ss[1] == 0xFF && ss[2] == 0x00)   {    reVal = Encoding.BigEndianUnicode;   }   else if (ss[0] == 0xFF && ss[1] == 0xFE && ss[2] == 0x41)   {    reVal = Encoding.Unicode;   }   else   {    if (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF)    {     reVal = Encoding.UTF8;    }    else    {     int i;     int.TryParse(fs.Length.ToString(), out i);     ss = r.ReadBytes(i);     if (IsUTF8Bytes(ss))      reVal = Encoding.UTF8;    }   }   r.Close();   return reVal;  }  /// <summary>   /// 判斷是否是不帶 BOM 的 UTF8 格式   /// </summary>   /// <param name="data"></param>   /// <returns></returns>   private static bool IsUTF8Bytes(byte[] data)  {   int charByteCounter = 1;　 //計算當前正分析的字符應還有的字節數    byte curByte; //當前分析的字節.    for (int i = 0; i < data.Length; i++)   {    curByte = data[i];    if (charByteCounter == 1)    {     if (curByte >= 0x80)     {      //判斷當前       while (((curByte <<= 1) & 0x80) != 0)      {       charByteCounter++;      }      //標記位首位若為非0 則至少以2個1開始 如:110XXXXX...........1111110X　       if (charByteCounter == 1 || charByteCounter > 6)      {       return false;      }     }    }    else    {     //若是UTF-8 此時第一位必須為1      if ((curByte & 0xC0) != 0x80)     {      return false;     }     charByteCounter--;    }   }   if (charByteCounter > 1)   {    throw new Exception("非預期的byte格式!");   }   return true;  } }