在.NET 3.5下创建的WinForm程序调用Core 3.0 Web API时出现“IOException: 由于远程方已关闭传输流，身份验证失败”错误

HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(serviceUrl);
HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();//IOException: 由于远程方已关闭传输流，身份验证失败。

错误详细：

System.Net.WebException
HResult=0x80131509
Message=基础连接已经关闭: 发送时发生错误。
Source=<无法计算异常源>
StackTrace:
<无法计算异常堆栈跟踪>

内部异常 1:
IOException: 由于远程方已关闭传输流，身份验证失败。

View Code

解决办法：

HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(serviceUrl);
ServicePointManager.SecurityProtocol = (SecurityProtocolType)192 | (SecurityProtocolType)768 | (SecurityProtocolType)3072;
//4.5版本以上可使用：ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11;
HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();

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参考：

https://codeday.me/bug/20180824/224009.html

https://www.cnblogs.com/merray/p/6364863.html