C#读取文件时自动判断编码函数

         /// <summary>
        /// C#读取文件时自动判断编码函数
        /// </summary>
        /// <param name="FILE_NAME">需要判断编码方式文件的物理路径

如"C:\file\file.txt"</param>
        /// <returns></returns>
        public static System.Text.Encoding GetType(string FILE_NAME)
        {
            FileStream fs = new FileStream(FILE_NAME, FileMode.Open,

FileAccess.Read);
            System.Text.Encoding r = GetType(fs);
            fs.Close();
            return r;
        }

        public static System.Text.Encoding GetType(FileStream fs)
        {
            /*byte[] Unicode=new byte[]{0xFF,0xFE}; 
            byte[] UnicodeBIG=new byte[]{0xFE,0xFF}; 
            byte[] UTF8=new byte[]{0xEF,0xBB,0xBF};*/

            BinaryReader r = new BinaryReader(fs,

System.Text.Encoding.Default);
            byte[] ss = r.ReadBytes(4);
            r.Close();
            //编码类型 Coding=编码类型.ASCII;  
            if (ss[0] <= 0xEF)
            {
                if (ss[0] == 0xEF && ss[1] == 0xBB && ss[2] == 0xBF)
                {
                    return System.Text.Encoding.UTF8;
                }
                else if (ss[0] == 0xFE && ss[1] == 0xFF)
                {
                    return System.Text.Encoding.BigEndianUnicode;
                }
                else if (ss[0] == 0xFF && ss[1] == 0xFE)
                {
                    return System.Text.Encoding.Unicode;
                }
                else
                {
                    return System.Text.Encoding.Default;
                }
            }
            else
            {
                return System.Text.Encoding.Default;
            }
        }