Had a certificate expire at 8PM EST tonight on a critical project I was supposed to demo, wasn’t going to stop me… lots of articles don’t really go over how to do this now on .NET Core 1.0, so lets cover the code to do so:

using (var httpClientHandler = new HttpClientHandler())
{
   httpClientHandler.ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => { return true; };
   using (var client = new HttpClient(httpClientHandler))
   {
       // Make request here.
   }
}

Pretty simple, really.