.net4.0 请求HTTPS出错：未能创建 SSL/TLS 安全通道

两种方法：

1.在代码中修改

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;// SecurityProtocolType.Tls1.2;

2.修复注册表

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]"SchUseStrongCrypto"=dword:00000001

https://stackoverflow.com/questions/33761919/tls-1-2-in-net-framework-4-0
https://blogs.msdn.microsoft.com/jchiou/2016/05/27/%E5%A6%82%E4%BD%95%E5%9C%A8-net-framework-4-0-4-5-%E4%BB%A5%E4%B8%8A%E7%9A%84%E7%A8%8B%E5%BC%8F%E6%94%AF%E6%8F%B4-tls-1-2/

.net4.0 请求HTTPS出错：未能创建 SSL/TLS 安全通道

原文地址：https://www.cnblogs.com/yczz/p/9419019.html