Problem solving SSL https request process

A recent project uses the https request, before the discovery in the course of the actual call http method does not support https, calls have been an error.

Query a bit, add a few lines of code to solve the problem.

 public string HttpPost(string Url, string postDataStr, string useragent = null)
        {
            ServicePointManager.ServerCertificateValidationCallback += (s, cert, chain, sslPolicyErrors) => true;//新增一行
            System.Net.ServicePointManager.SecurityProtocol = (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;//新增第二行，很重要
            ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(CheckValidationResult);//新增第三行
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = Encoding.UTF8.GetByteCount(postDataStr);
            if (!string.IsNullOrEmpty(useragent))
            {
                request.UserAgent = useragent;
            }
            Stream myRequestStream = request.GetRequestStream();
            StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("gb2312"));
            myStreamWriter.Write(postDataStr);
            myStreamWriter.Close();

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();


            Stream myResponseStream = response.GetResponseStream();
            StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));
            string retString = myStreamReader.ReadToEnd();
            myStreamReader.Close();
            myResponseStream.Close();

            return retString;
        }