如何在.NET中猜测没有BOM的文件的编码？

using System;
using System.IO;
using System.Text;

public class EncodingDetector
{
    public static Encoding DetectEncoding(string filePath)
    {
        // 获取文件的前4个字节
        byte[] bom = new byte[4];
        using (FileStream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
        {
            fs.Read(bom, 0, 4);
        }

        // 检测BOM
        if (bom[0] == 0xef && bom[1] == 0xbb && bom[2] == 0xbf)
        {
            return Encoding.UTF8;
        }
        else if (bom[0] == 0xfe && bom[1] == 0xff)
        {
            return Encoding.BigEndianUnicode;
        }
        else if (bom[0] == 0xff && bom[1] == 0xfe)
        {
            if (bom[2] == 0 && bom[3] == 0)
            {
                return Encoding.UTF32;
            }
            else
            {
                return Encoding.Unicode;
            }
        }
        else if (bom[0] == 0x2b && bom[1] == 0x2f && bom[2] == 0x76)
        {
            return Encoding.UTF7;
        }
        else
        {
            // 如果没有BOM，则尝试检测编码
            using (StreamReader reader = new StreamReader(filePath, Encoding.Default, true))
            {
                reader.Read();
                return reader.CurrentEncoding;
            }
        }
    }
}