关于字符集:自动根据文本文件的字符集编码加载文件内容字符串

主动依据文本文件的字符集编码加载文件内容字符串，并反对按原始编码格局再次写入。

using System;using System.IO;using System.Linq;using System.Text;/// <summary> /// 获取文件的编码格局 /// </summary> public class TextEncode{    public Encoding Encoding { get; private set; }    public byte[] BOM { get; private set; }    public string ReadText(string fileName, out Encoding enc)    {        var r = ReadText(fileName);        enc = Encoding;        return r;    }    public string ReadText(string fileName)    {        Encoding encoding = null;        byte[] bytes = File.ReadAllBytes(fileName);        int bomLen = 0;        if (bytes.Length > 1)        {            if (bytes[0] == 0xFE && bytes[1] == 0xFF) //UTF-16（大端序）            {                encoding = new UnicodeEncoding(true, true);                bomLen = 2;            }            else if (bytes[0] == 0xFF && bytes[1] == 0xFE) //UTF-16（小端序）            {                encoding = new UnicodeEncoding(false, true);                bomLen = 2;            }        }        if (encoding == null && bytes.Length > 2)        {            if ((bytes[0] == 0xEF && bytes[1] == 0xBB && bytes[2] == 0xBF)) //UTF-8            {                encoding = new UTF8Encoding(true);                bomLen = 3;            }        }        if (encoding == null && bytes.Length > 3)        {            if (bytes[0] == 0x00 && bytes[1] == 0x00 && bytes[2] == 0xFE && bytes[3] == 0xFF) //UTF-32（大端序）            {                encoding = new UTF32Encoding(true, true);                bomLen = 4;            }            else if (bytes[0] == 0xFF && bytes[1] == 0xFE && bytes[2] == 0x00 && bytes[3] == 0x00) //UTF-32（小端序）            {                encoding = new UTF32Encoding(false, true);                bomLen = 4;            }        }        if (encoding == null && IsUTF8Bytes(bytes))        {            encoding = Encoding.UTF8; //UTF8无BOM        }        if (encoding == null) encoding = Encoding.Default;        Encoding = encoding;        BOM = new byte[bomLen];        Array.Copy(bytes, BOM, bomLen);        return encoding.GetString(bytes, bomLen, bytes.Length - bomLen);    }    /// <summary>     /// 判断是否是不带 BOM 的 UTF8 格局     /// </summary>     /// <param name="data"></param>     /// <returns></returns>     private bool IsUTF8Bytes(byte[] data)    {        int charByteCounter = 1; //计算以后正剖析的字符应还有的字节数         byte curByte; //以后剖析的字节.         for (int i = 0; i < data.Length; i++)        {            curByte = data[i];            if (curByte == 0) throw new FormatException("非预期的byte格局");            if (charByteCounter == 1)            {                if (curByte >= 0x80)                {                    //判断以后                     while (((curByte <<= 1) & 0x80) != 0)                    {                        charByteCounter++;                    }                    //标记位首位若为非0 则至多以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 FormatException("非预期的byte格局");        }        return true;    }    /// <summary>    /// 已雷同的Encoding和BOM再次写入    /// </summary>    public void WriteBySameEncoding(string fileName, string content)    {        if (BOM == null)        {            throw new Exception("须要先调用ReadText办法");        }        using (var file = File.Create(fileName))        {            file.Write(BOM, 0, BOM.Length);            var bytes = Encoding.GetBytes(content);            file.Write(bytes, 0, bytes.Length);        }    }}