Why my client could not establish trust relationship for the SSL/TLS secure channel with authority?

Question

When I am trying consuming a Web Service with a URL HTTPS it is causing this error message:

[SecurityNegotiationException: Could not establish trust relationship for the SSL/TLS secure channel with authority.

I have already read a solution to accept this trust between my client program (C#) and the HTTPS address:

System.Net.ServicePointManager.ServerCertificateValidationCallback += (sender, certificate, chain, sslPolicyErrors) => { return true; };

So my question is why my client could not establish trust relationship for the SSL/TLS secure channel with authority? Does somebody know? Because it seems that this solution is not safe.

Answer 1

If you are using .NET core, you can set CertificateValidationMode = X509CertificateValidationMode.None and RevocationMode nocheck

client.ClientCredentials.ServiceCertificate.SslCertificateAuthentication =
    new X509ServiceCertificateAuthentication()
    {
        CertificateValidationMode = X509CertificateValidationMode.None,
        RevocationMode = System.Security.Cryptography.X509Certificates.X509RevocationMode.NoCheck
    };