Occasionally encountered "the request was aborted:could not create SSL/TLS secure channel." How to solve?

The project involves invoking the webservice of the third-party HTTPS, and I am using the original HttpWebRequest.

The code has taken into account the HTTPS, plus the SSL3 protocol, plus the delegate invocation. But occasionally, I still come across

The request was aborted:could not create the SSL/TLS secure channel.

Such a mistake.

So according to this blog, change it to use the TLS protocol to see if there is any use.

            if (URL. StartsWith ("https", StringComparison.OrdinalIgnoreCase))///https request            {                Servicepointmanager.expect100continue = true;                Servicepointmanager.securityprotocol = Securityprotocoltype.tls; SSL3 protocol replaced with TLS protocol                servicepointmanager.servercertificatevalidationcallback = new Remotecertificatevalidationcallback (CheckValidationResult);                webRequest = webrequest.create (URL) as HttpWebRequest;                Webrequest.protocolversion = Httpversion.version10;            }            else            {                webRequest = webrequest.create (URL) as HttpWebRequest;            }

　　

Occasionally encountered "the request was aborted:could not create SSL/TLS secure channel." How to solve?