GetAccessToken_ClientCertificateCredential.cs

public async Task<string> GetAccessTokenAsync(string resourceUrl, string tenantId, string clientId, string pfxCertDirPath, string pfxCertPassword)
{
    var clientCertificate = new X509Certificate2(pfxCertDirPath, pfxCertPassword);

    var credential = new ClientCertificateCredential(tenantId, clientId, clientCertificate);

    var accessToken = await credential.GetTokenAsync(new TokenRequestContext(scopes: [resourceUrl + "/.default"]) { });

    return accessToken.Token;
}