public static string HttpPost(string url, string jsonStr)
        {
            HttpWebRequest request = null;
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Ssl3
                | (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;
            ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback((sender, certificate, chain, errors) => true);//驗證服務(wù)器證書回調(diào)自動驗證
            try
            {
                request = (HttpWebRequest)WebRequest.Create(url);//創(chuàng)建一個HTTP請求
            }
            catch (Exception ex)
            {
                Console.WriteLine("Http Post請求 創(chuàng)建失敗！" + ex.Message);
                //throw new Exception("Http請求創(chuàng)建失敗", ex);
                return null;
            }
            request.Method = "POST";//Post請求方式 
            request.ContentType = "application/json";//內(nèi)容類型
            request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.80 Safari/537.36";

            byte[] byteArray;//設(shè)置參數(shù)，并進行URL編碼
            if (jsonStr == null)
            {
                jsonStr = "";
            }
            byteArray = System.Text.Encoding.UTF8.GetBytes(jsonStr);//將Json字符串轉(zhuǎn)化為字節(jié)byte數(shù)組
            request.ContentLength = byteArray.Length;//設(shè)置請求的ContentLength
            Stream writer;
            try
            {
                writer = request.GetRequestStream();//獲取用于寫入請求數(shù)據(jù)的Stream對象
            }
            catch (Exception ex)
            {
                Console.WriteLine("獲取Http請求寫入流失敗!" + ex.Message);
                return null;
            }
            writer.Write(byteArray, 0, byteArray.Length);//將請求參數(shù)寫入流
            writer.Close();//關(guān)閉請求流
            HttpWebResponse response;
            try
            {
                response = (HttpWebResponse)request.GetResponse();//獲得響應(yīng)流
            }
            catch (WebException ex)
            {
                Console.WriteLine("獲取Http響應(yīng)流失敗!" + ex.Message);
                return null;
            }
            Stream responseStream = response.GetResponseStream();
            StreamReader streamReader = new StreamReader(responseStream, Encoding.GetEncoding("UTF-8"));
            string postContent = streamReader.ReadToEnd();
            streamReader.Close();
            return postContent;//Post請求后服務(wù)器返回的數(shù)據(jù)
        }
    }