C#判断文件编码格式

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

namespace EncodingIdentifier
{
    public class Text
    {
        public static Encoding GetEncodingType(string fileName)
        {
            FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
            BinaryReader binary = new BinaryReader(fileStream, Encoding.Default);
            byte[] bytes = binary.ReadBytes(3);
            fileStream.Close();
            if (bytes[0] >= 0xEF)
            {
                if (GetResult(bytes, 0, 0xEF) && GetResult(bytes, 1, 0xBB) && GetResult(bytes, 2, 0xBF))
                {
                    return Encoding.UTF8;
                }
                else if (GetResult(bytes, 0, 0xFE) && GetResult(bytes, 1, 0xFF))
                {
                    return Encoding.BigEndianUnicode;
                }
                else if (GetResult(bytes, 0, 0xFF) && GetResult(bytes, 1, 0xFE))
                {
                    return Encoding.Unicode;
                }
                else
                {
                    return Encoding.Default;
                }
            }
            else
            {
                return Encoding.Default;
            }
        }

        public static Encoding GetEncodingType(FileStream fileStream)
        {
            BinaryReader binary = new BinaryReader(fileStream, Encoding.Default);
            byte[] bytes = binary.ReadBytes(3);
            if (bytes[0] >= 0xEF)
            {
                if (GetResult(bytes, 0, 0xEF) && GetResult(bytes, 1, 0xBB) && GetResult(bytes, 2, 0xBF))
                {
                    return Encoding.UTF8;
                }
                else if (GetResult(bytes, 0, 0xFE) && GetResult(bytes, 1, 0xFF))
                {
                    return Encoding.BigEndianUnicode;
                }
                else if (GetResult(bytes, 0, 0xFF) && GetResult(bytes, 1, 0xFE))
                {
                    return Encoding.Unicode;
                }
                else
                {
                    return Encoding.Default;
                }
            }
            else
            {
                return Encoding.Default;
            }
        }

        public static bool GetResult(byte[] Value, int index, int judge)
        {
            return Value.Length > index ? Value[index] == judge : false;
        }
    }
}