Post xml string to https url in C#

Hi Experts,
i need to send an xml string to a https url
here is the code i ham trying with
                string strXMLToPost = "<?xml version="1.0" encoding="UTF-8"?><methodCall>........</methodCall>";

                X509Certificate cert = X509Certificate.CreateFromCertFile("E:\\CERTIFICATES\\za.crt");

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://.........");
                request.Method = "POST";
                request.ContentTyp ...