(.NET Core C#) FTP Connect, Examine Server Certificate, and then Authenticate

Demonstrates how to connect to an FTP server, examine the server's SSL/TLS certificate, and then, if it meets the application's security requirements, proceed to authenticate.

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// This example assumes Chilkat Ftp2 to have been previously unlocked.
// See Unlock Ftp2 for sample code.

Chilkat.Ftp2 ftp = new Chilkat.Ftp2();

ftp.Hostname = "www.authtls-ftps-server.com";
ftp.Username = "FTP_LOGIN";
ftp.Password = "FTP_PASSWORD";
ftp.AuthTls = true;
ftp.Port = 21;

// Connect to the FTP server using explicit TLS (AUTH TLS).
bool success = ftp.ConnectOnly();
if (success != true) {
    Debug.WriteLine(ftp.LastErrorText);
    return;
}

// Get the FTP server's certificate.
Chilkat.Cert serverCert = ftp.GetSslServerCert();
if (ftp.LastMethodSuccess != true) {
    Debug.WriteLine(ftp.LastErrorText);
    return;
}

// Now that we have the certificate, we can check it in any way we desire.
// (See the online reference documentation for the certificate object's methods
// and properties)...

// Assuming the certificate is OK, proceed to authenticate with the FTP server.
success = ftp.LoginAfterConnectOnly();
if (success != true) {
    Debug.WriteLine(ftp.LastErrorText);
    return;
}

// 
// Proceed with uploading/download files, etc...
// 

ftp.Disconnect();
Debug.WriteLine("Success.");