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【CSharp】读取文件自动区分GB2312和UTF8

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本文字数： 3.1k 阅读时长 ≈ 3 分钟

https://www.cnblogs.com/guyun/p/4262587.html

C# 获取文本文件的编码，自动区分GB2312和UTF8

以下是获取文件编码的一个类

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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace iPaaS_KBS_API.Helper
{
    /// <summary>
    /// 获取文件的编码格式
    /// </summary>
    public class EncodingType
    {
        /// <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;
        }
    }
}

调用方式：

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private void txtMenuOpen_Click(object sender, EventArgs e)
{
    string fName;
    OpenFileDialog openFileDialog = new OpenFileDialog();
    openFileDialog.InitialDirectory = "";//注意这里写路径时要用c:而不是c:
    openFileDialog.Filter = "文本文档|*.txt";
    openFileDialog.RestoreDirectory = true;
    openFileDialog.FilterIndex = 1;
    if (openFileDialog.ShowDialog() == DialogResult.OK)
    {
        fName = openFileDialog.FileName;

        txtBox.Text = System.IO.File.ReadAllText(fName,
        FileEncoding.EncodingType.GetType(fName));
    }
}

编码查询

https://www.filesignatures.net/index.php?page=all