如何在C#中验证webhook的RS256签名属性？

using System;
using System.Text;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Security;

public class WebhookValidator
{
    public static bool ValidateWebhook(string payload, string signature, string publicKey)
    {
        try
        {
            byte[] signatureBytes = Convert.FromBase64String(signature);

            PemReader pemReader = new PemReader(new StringReader(publicKey));
            AsymmetricKeyParameter publicKeyParameter = (AsymmetricKeyParameter)pemReader.ReadObject();

            ISigner signer = SignerUtilities.GetSigner("SHA256withRSA");
            signer.Init(false, publicKeyParameter);
            byte[] payloadBytes = Encoding.UTF8.GetBytes(payload);
            signer.BlockUpdate(payloadBytes, 0, payloadBytes.Length);

            return signer.VerifySignature(signatureBytes);
        }
        catch (Exception ex)
        {
            Console.WriteLine("Webhook verification failed: " + ex.Message);
            return false;
        }
    }
}