由于以下错误消息，我们无法使用WebRequest连接到HTTPS服务器:
请求被中止:无法创建SSL/TLS安全通道。
我们知道服务器没有有效的HTTPS证书，但为了绕过这个问题，我们使用下面的代码，我们从另一个StackOverflow帖子:
private void Somewhere() {
ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(AlwaysGoodCertificate);
}
private static bool AlwaysGoodCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors policyErrors) {
return true;
}
问题是服务器从未验证证书，并出现上述错误而失败。有人知道我该怎么做吗?
我应该提到的是，我和一个同事几周前进行了测试，它运行得很好，与我上面写的类似。我们发现的唯一“主要区别”是，我用的是Windows 7，而他用的是Windows XP。这会改变什么吗?
Another possible cause of the The request was aborted: Could not create SSL/TLS secure channel error is a mismatch between your client PC's configured cipher_suites values, and the values that the server is configured as being willing and able to accept. In this case, when your client sends the list of cipher_suites values that it is able to accept in its initial SSL handshaking/negotiation "Client Hello" message, the server sees that none of the provided values are acceptable, and may return an "Alert" response instead of proceeding to the "Server Hello" step of the SSL handshake.
为了研究这种可能性，您可以下载Microsoft Message Analyzer，并使用它来跟踪当您尝试建立到服务器的HTTPS连接失败时(在c#应用程序中)发生的SSL协商。
如果您能够从另一个环境(例如您提到的Windows XP机器)成功建立HTTPS连接，或者可能通过在不使用操作系统加密套件设置的非微软浏览器(如Chrome或Firefox)中点击HTTPS URL，则在该环境中运行另一个Message Analyzer跟踪，以捕获SSL协商成功时发生的情况。
希望您能看到两个Client Hello消息之间的一些区别，从而能够准确地指出失败的SSL协商是什么原因导致它失败的。然后，您应该能够对Windows进行配置更改，以使其成功。IISCrypto是一个很好的工具(即使对于客户端pc，尽管它叫“IIS”)。
以下两个Windows注册表项控制你的电脑将使用的cipher_suites值:
微软HKLM \ SOFTWARE \政策\ \ SSL加密\ Configuration \ \ 00010002
HKLM \ SYSTEM \ CurrentControlSet \ \控制密码学\ \当地\ SSL配置\ 00010002
以下是我如何调查和解决这种无法创建SSL/TLS安全通道问题的实例的完整记录:http://blog.jonschneider.com/2016/08/fix-ssl-handshaking-error-in-windows.html
After days of pulling what hair I have left out, we solved the problem. I tried everything suggested on this post and nothing worked for me. For us, we had a basic .Net Framework 4.8 console app running on a customers Windows VM. The on-premise server we were communicating with required that SSL Certificate Validation was turned off. One of our guys discovered that the server required we were using TLS 1.0 and on the registry settings of the VM, TLS 1.0 was disabled. Once we enabled that, it worked. I also needed to added the following two lines as mentioned many times above:
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
