asp.net - 底层连接关闭问题：底层连接已关闭：发送时发生意外错误

Question

我得到了这个例外。

  The underlying connection was closed: An unexpected error occurred on a send.

我已经尝试了很多方法（ServicePointManager.Expect100Continue = true; ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3; 和 keepalive 方法）。问题仍然没有解决。谁能帮我解决问题？

 public static string FunGetURLShortening(string strLargeURL)
    {
        string strShortURL = "";

        string strAPI = ConfigurationManager.AppSettings["API"].ToString();

        //var request = (HttpWebRequest)WebRequest.Create(strAPI);
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(strAPI);
        request.KeepAlive = true;

        string strName = ConfigurationManager.AppSettings["ReqParaName"].ToString();


        string strReqParameter = "name=" + strName + "&" + "url=" + strLargeURL;
        byte[] data = Encoding.UTF8.GetBytes(strReqParameter);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = data.Length;
        request.ProtocolVersion = HttpVersion.Version10;
        //ServicePointManager.Expect100Continue = true;
        //ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
        //ServicePointManager.SecurityProtocol = (SecurityProtocolType)48 | (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;
        //| SecurityProtocolType.Tls;
        //System.Net.ServicePointManager.SecurityProtocol = (SecurityProtocolType)0x00000C00;

        using (var stream = request.GetRequestStream())
        {
            stream.Write(data, 0, data.Length);
        }
        try
        {
            var response = (HttpWebResponse)request.GetResponse();
            string responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();
            JavaScriptSerializer serial = new JavaScriptSerializer();
            serial.MaxJsonLength = Int32.MaxValue;
            var ResponsePara = serial.Deserialize<ResponseParameters>(responseString);
            if (ResponsePara.status == "1")
            {
                strShortURL = ResponsePara.data;

            }
            else
            {
                strShortURL = strLargeURL;
            }

        }

        catch (Exception ex)
        {
            ErrorLog.WriteErrorLog(strLogFilePath, "Error:- " + ex.Message.ToString());
        }
        return strShortURL;
    }