C#发送HTTPS请求：基础连接已经关闭: 发送时发生错误

出现这个问题，一直很恼火！！！
主要是之前一直采用http发送请求没有问题，修改成https就有问题了！！！
于是就考虑到，https协议问题？？？

解决办法

   //添加https兼容处理
   HttpWebRequest request = null;
   if (serviceAddress.StartsWith("https", StringComparison.OrdinalIgnoreCase))
   {
    
    
       // 这里设置了协议类型。把SSL验证的设置写到HttpRequect创建之前
       ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
       ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
       ServicePointManager.CheckCertificateRevocationList = true;
       ServicePointManager.DefaultConnectionLimit = 100;
       ServicePointManager.Expect100Continue = true;

       request = WebRequest.Create(serviceAddress) as HttpWebRequest;
       request.ProtocolVersion = HttpVersion.Version11;
       request.KeepAlive = false;
   }
   else
   {
    
    
       request = (HttpWebRequest)WebRequest.Create(serviceAddress);
   }

重点：

1. 添加https协议设置
2. 把SSL验证的设置写到HttpRequect创建之前

详细请查阅如下：
https://blog.csdn.net/qq_16771097/article/details/120786063