Using a x509 Client Certificate to authenticate against a REST Service

Does anyone know the best way to implement accessing a REST service which has a Client Certificate

I've tried both WebRequestHandler to add the certificate, but mono does not seem to support this and the application won't run. I have also tried HttpClientHandler.

Code snippet below :
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
X509Certificate2 certificate = App.CertificateFile;
var handler = new WebRequestHandler
{
ClientCertificateOptions = ClientCertificateOption.Manual
};
handler.ClientCertificates.Add(certificate);
var client = new HttpClient(handler);