如何在不使用SignedXml的情况下在c#中验证xml数字签名？

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.Xml;
using System.Xml;

public class XmlSignatureValidator
{
    public bool VerifyXmlSignature(string xmlFilePath)
    {
        try
        {
            // 加载XML文档
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.PreserveWhitespace = true;
            xmlDoc.Load(xmlFilePath);

            // 提取数字签名
            XmlNodeList signatureNodes = xmlDoc.GetElementsByTagName("Signature", "http://www.w3.org/2000/09/xmldsig#");
            if (signatureNodes.Count == 0)
            {
                // 没有找到数字签名
                return false;
            }

            // 提取证书
            XmlNodeList x509CertNodes = xmlDoc.GetElementsByTagName("X509Certificate", "http://www.w3.org/2000/09/xmldsig#");
            if (x509CertNodes.Count == 0)
            {
                // 没有找到证书
                return false;
            }

            // 提取证书信息
            X509Certificate2 cert = new X509Certificate2(Convert.FromBase64String(x509CertNodes[0].InnerText));

            // 验证签名
            SignedXml signedXml = new SignedXml(xmlDoc);
            signedXml.LoadXml((XmlElement)signatureNodes[0]);

            RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)cert.PublicKey.Key;
            bool isValid = signedXml.CheckSignature(rsa);

            return isValid;
        }
        catch (Exception ex)
        {
            // 处理异常
            Console.WriteLine("验证XML数字签名时出错：" + ex.Message);
            return false;
        }
    }
}