c#呼び出しSSL

X509Store store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
X509Certificate2Collection certs = X509Certificate2UI.SelectFromCollection(store.Certificates, "Certificates", "Please select certificate to use", X509SelectionFlag.SingleSelection);
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://localhost:8443/axis/");
request.ClientCertificates.Add(certs[0]);
request.KeepAlive = true;
request.Method = "POST";
request.ContentType = "text/xml";
request.KeepAlive = true;                
HttpWebResponse res = (HttpWebResponse)request.GetResponse();
StreamReader sr = new StreamReader(res.GetResponseStream());
MessageBox.Show(sr.ReadToEnd());