C#读取文档小工具

C#读取文件,牵扯到编码格式,这里面也有学问(System.IO),编码格式在微软官方技术文档里,我粗略看了下,也有几十种:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace winFtn6
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btn_tn6_Click(object sender, EventArgs e)
        {
          
                OpenFileDialog openFileDialog = new OpenFileDialog();
                openFileDialog.InitialDirectory = "c:\";//注意这里写路径时要用c:\而不是c:
                openFileDialog.Filter = "文本文件|*.*|C#文件|*.cs|所有文件|*.*";
                openFileDialog.RestoreDirectory = true;
                openFileDialog.FilterIndex = 1;
                if (openFileDialog.ShowDialog() == DialogResult.OK)
                {
                   string fName = openFileDialog.FileName;

                System.Text.Encoding type = GetType(fName);
                //文本：GB2312，
                string text = File.ReadAllText(fName, System.Text.Encoding.GetEncoding("GB2312"));
                richTextBox1.Text = type.ToString()+"readalltext:"+ text;
                // richTextBox1.AppendText("");
                ///

             
            }
            
        }
        /// <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;
        }

    }
}