namespace System.Net.Security
{
    public delegate X509Certificate LocalCertificateSelectionCallback(object sender, string targetHost, X509CertificateCollection localCertificates, X509Certificate remoteCertificate, string[] acceptableIssuers);
    {
        public virtual X509Certificate Invoke(object sender, string targetHost, X509CertificateCollection localCertificates, X509Certificate remoteCertificate, string[] acceptableIssuers);
    }
}