/// <summary>

        /// 指定Post地址使用Get 方式获取全部字符串

        /// </summary>

        /// <param name="url">请求后台地址</param>

        /// <param name="content">Post提交数据内容(utf-8编码的)</param>

        /// <returns></returns>

        public static string PostSsl3(string url, string content)

        {

            string path = @"D:\Site\QL.Back.API\wwwroot\file\cert\apiclient_cert.p12";

            string password = "xxxx";

            //HttpClient请求，在handler里添加X509Certificate2 证书，数据data是byte[] 类型，所以需要使用ByteArrayContent传入

            var handler = new HttpClientHandler();

            handler.ClientCertificateOptions = ClientCertificateOption.Manual;

            handler.SslProtocols = SslProtocols.Tls12;

            //获取证书路径

            //商户私钥证书，用于对请求报文进行签名

            handler.ClientCertificates.Add(new X509Certificate2(path, password, X509KeyStorageFlags.PersistKeySet | X509KeyStorageFlags.MachineKeySet));

            handler.SslProtocols = SslProtocols.Tls12 | SslProtocols.Tls11 | SslProtocols.Tls;

            handler.ServerCertificateCustomValidationCallback = (message, cert, chain, errors) => true;

            //post请求

            var client = new HttpClient(handler);

            using (MemoryStream ms = new MemoryStream())

            {

                byte[] bytes = Encoding.UTF8.GetBytes(content);

                ms.Write(bytes, , bytes.Length);

                ms.Seek(, SeekOrigin.Begin);//设置指针读取位置，否则发送无效

                HttpContent hc = new StreamContent(ms);

                var response = client.PostAsync(url, hc).Result;

                return response.Content.ReadAsStringAsync().Result;

            }

        }