C httpwebrequest Access HTTPS Error Handling Method

C # httpwebrequest encountered this error while accessing the HTTPS link, but if I open a packet grabbing tool, such as filddler2, POST returns to normal

The Message of the error prompt is:

The underlying connection is closed: An error occurred while sending.

InnerException is:

An unexpected EOF or 0 bytes was received from the transport stream.

I tried N methods on the Internet, and the following is the solution this time:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;

List the solutions found online under 1, and you may be able to solve your problem

Here are the solutions found online:

1. request.ProtocolVersion = HttpVersion.Version10;

2. ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);

3.ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;

4. Try changing to UserAgent

5. Add the following to App. config:

<system.net>
  <settings>
   <httpWebRequest useUnsafeHeaderParsing="true"/>
  </settings>
 </system.net>