c# - 如何在 C# 中向 TLS 1.2 w 启用前向保密的服务器发送请求？

Question

对启用 TLS 1.2 的服务器的请求可以使用以下代码正常工作。它不适用于启用前向保密。收到“无法创建 SSL/TLS 通道”异常。这是代码，

ServicePointManager.Expect100Continue = true;
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
                       | SecurityProtocolType.Tls11
                       | SecurityProtocolType.Tls12
                       | SecurityProtocolType.Ssl3;
 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(targetUrl);           
request.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) =>
            {
                if (certificate != null)
                {
                    requestDetails += $" ServerCertificateValidationCallback: {certificate.ToString(true)}";
                }
                requestDetails += $" SslPolicyErrors: {sslPolicyErrors}";
                return true;
            };

有人可以帮忙吗？