Get Client Certificate

using System;
using System.Net;
using System.Security.Cryptography.X509Certificates;

class MainClass {
    public static void Main() {

        WebRequest MyWebRequestA = WebRequest.Create("http://www.Mysite.com");
        MyWebRequestA.Credentials = new NetworkCredential("userName", "password");
        MyWebRequestA.PreAuthenticate = true;
        WebRequest MyWebRequestB = WebRequest.Create("http://www.Mysite.com");
        MyWebRequestB.Credentials = CredentialCache.DefaultCredentials;
        MyWebRequestB.PreAuthenticate = true;

        HttpWebRequest requestC = (HttpWebRequest)WebRequest.Create("http://www.Mysite.com");
        X509Certificate cert1 = X509Certificate.CreateFromCertFile("TestCertificate.cer");
        requestC.ClientCertificates.Add(cert1);
        HttpWebRequest requestD = (HttpWebRequest)WebRequest.Create("http://www.Mysite.com");
        X509Store store = new X509Store();
        X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindBySubjectName,"Joe", false);

        if (certs.Count == 1) {
            requestD.ClientCertificates.Add(certs[0]);
        } else {
            certs = X509Certificate2UI.SelectFromCollection(
                store.Certificates,
                "Select Certificate",
                "Select the certificate to use for authentication.",
                X509SelectionFlag.SingleSelection);

            if (certs.Count != 0) {
                requestD.ClientCertificates.Add(certs[0]);
            }
        }
    }
}