FileUtilty

 class FileUtility
    {
        /// <summary> 
        /// 给定文件的路径，读取文件的二进制数据，判断文件的编码类型 
        /// </summary> 
        /// <param name="FILE_NAME">文件路径</param> 
        /// <returns>文件的编码类型</returns> 
        public static System.Text.Encoding GetType(string FILE_NAME)
        {
            FileStream fs = new FileStream(FILE_NAME, FileMode.Open, FileAccess.Read);
            Encoding r = GetType(fs);
            fs.Close();
            return r;
        }

        /// <summary> 
        /// 通过给定的文件流，判断文件的编码类型 
        /// </summary> 
        /// <param name="fs">文件流</param> 
        /// <returns>文件的编码类型</returns> 
        public static System.Text.Encoding GetType(FileStream fs)
        {
            byte[] Unicode = new byte[] { 0xFF, 0xFE, 0x41 };
            byte[] UnicodeBIG = new byte[] { 0xFE, 0xFF, 0x00 };
            byte[] UTF8 = new byte[] { 0xEF, 0xBB, 0xBF }; //带BOM 
            Encoding reVal = Encoding.Default;

            BinaryReader r = new BinaryReader(fs, System.Text.Encoding.Default);
            int i;
            int.TryParse(fs.Length.ToString(), out i);
            byte[] ss = r.ReadBytes(i);
            if (IsUTF8Bytes(ss) || (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF))
            {
                reVal = Encoding.UTF8;
            }
            else 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;
            }
            r.Close();
            return reVal;

        }

        /// <summary> 
        /// 判断是否是不带 BOM 的 UTF8 格式 
        /// </summary> 
        /// <param name="data"></param> 
        /// <returns></returns> 
        private static bool IsUTF8Bytes(byte[] data)
        {
            int charByteCounter = 1;
            //计算当前正分析的字符应还有的字节数 
            byte curByte; //当前分析的字节. 
            for (int i = 0; i < data.Length; i++)
            {
                curByte = data[i];
                if (charByteCounter == 1)
                {
                    if (curByte >= 0x80)
                    {
                        //判断当前 
                        while (((curByte <<= 1) & 0x80) != 0)
                        {
                            charByteCounter++;
                        }
                        //标记位首位若为非0 则至少以2个1开始 如:110XXXXX...........1111110X　 
                        if (charByteCounter == 1 || charByteCounter > 6)
                        {
                            return false;
                        }
                    }
                }
                else
                {
                    //若是UTF-8 此时第一位必须为1 
                    if ((curByte & 0xC0) != 0x80)
                    {
                        return false;
                    }
                    charByteCounter--;
                }
            }
            if (charByteCounter > 1)
            {
                throw new Exception("非预期的byte格式");
            }
            return true;
        } 

    /// <summary>
    /// Converts a file from one encoding to another.
    /// </summary>
    /// <param name=”sourcePath”>the file to convert</param>
    /// <param name=”destPath”>the destination for the converted file</param>
    /// <param name=”sourceEncoding”>the original file encoding</param>
    /// <param name=”destEncoding”>the encoding to which the contents should be converted</param>

    public static void ConvertFileEncoding(String sourcePath, String destPath, Encoding sourceEncoding, Encoding destEncoding)
    {

        // If the destination’s parent doesn’t exist, create it.

        String parent = Path.GetDirectoryName(Path.GetFullPath(destPath));

        if (!Directory.Exists(parent))
        {
            Directory.CreateDirectory(parent);
        }

        // If the source and destination encodings are the same, just copy the file.
        if (sourceEncoding == destEncoding)
        {
            File.Copy(sourcePath, destPath, true);
            return;
        }

        // Convert the file.
        String tempName = null;

        try

        {
            tempName = Path.GetTempFileName();
            using (StreamReader sr = new StreamReader(sourcePath, sourceEncoding, false))

            {
                using (StreamWriter sw = new StreamWriter(tempName, false, destEncoding))
                {
                    int charsRead;
                    char[] buffer = new char[128 * 1024];
                    while ((charsRead = sr.ReadBlock(buffer, 0, buffer.Length)) > 0)
                    {
                        sw.Write(buffer, 0, charsRead);
                    }
                }

            }

            File.Delete(destPath);

            File.Move(tempName, destPath);

        }
        finally
        {
            File.Delete(tempName);
        }

    }


    }