class Program
    {
        static void Main(string[] args)
        {
            ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => 
            { 
                return false; 
            };

            Console.WriteLine("Send query...");
            try
            {
                WebClient client = new WebClient();
                client.DownloadString("https://<любой https-адрес/");
            }
            catch (Exception exception)
            {
                Console.WriteLine("Exception: {0}", exception.ToString());
            }
            Console.ReadLine();
        }
    }