When using WebClient to send request to a HTTPS site, if the site is using a self issued or expired Certificate, it will have the “Invalid Certification” error. So it has to handle that by disabling the SSL check.

System.Net.ServicePointManager.ServerCertificateValidationCallback =

 <span class="kwrd">new</span> System.Net.Security.RemoteCertificateValidationCallback(

     <span class="kwrd">delegate</span>

     { <span class="kwrd">return</span> <span class="kwrd">true</span>; }

 );