如何以编程方式检测和解码收到的.NET电子邮件中的文本编码为base64或其他？

using MailKit.Net.Imap;
using MailKit;
using MimeKit;
using System;
using System.Text;

class Program
{
    static void Main(string[] args)
    {
        using (var client = new ImapClient())
        {
            client.Connect("imap.example.com", 993, true);
            client.Authenticate("username", "password");

            var inbox = client.Inbox;
            inbox.Open(FolderAccess.ReadOnly);

            var message = inbox.GetMessage(0); // 获取第一封邮件

            // 解析Content-Type字段，确定编码方式
            var contentType = message.Body.ContentType;
            var encoding = Encoding.GetEncoding(contentType.Charset);

            // 解码邮件正文
            var body = message.TextBody;
            if (contentType.Encoding == ContentEncoding.Base64)
            {
                var base64Text = body.Replace("\r\n", ""); // 移除换行符
                var base64Bytes = Convert.FromBase64String(base64Text);
                body = encoding.GetString(base64Bytes);
            }

            Console.WriteLine(body);

            client.Disconnect(true);
        }
    }
}