.Net Core访问https接口报错：The requested security protocol is not supported

需要在设置协议类型前需要先设置协议版本信息，如下：

HttpWebRequestreq = (HttpWebRequest)HttpWebRequest.Create(url);

ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
//设置协议类型前设置协议版本
req.ProtocolVersion = HttpVersion.Version11;
//这里设置了协议类型。
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;

ServicePointManager.CheckCertificateRevocationList = true;
ServicePointManager.DefaultConnectionLimit = 1000;
ServicePointManager.Expect100Continue = false;

public bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
{
    return true;
}