System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception

Question

I'm using ASP.NET Core 2.2, in which I'm consuming secure API (e.g.https://google.com) from non-secure portal. But I am getting below error while requesting API :

System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception.

I have already tried with ServerCertificateCustomValidationCallback , ServerCertificateCustomValidationCallback, ServicePointManager.SecurityProtocol etc. but it didn't work.

When i am using ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Ssl3;, then I'm getting error:

System.NotSupportedException: The requested security protocol is not supported"

Sample code(s) which i have already tried ::

1.

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls   |
                                       SecurityProtocolType.Tls11 |
                                       SecurityProtocolType.Tls12 | 
                                       SecurityProtocolType.Ssl3;

2.

using (var httpClientHandler = new HttpClientHandler())
{
    httpClientHandler.ServerCertificateCustomValidationCallback =
        (message, cert, chain, errors) => { return true; };
    using (var client = new HttpClient(httpClientHandler))
    { // somecode }
}

3.

var handler = new HttpClientHandler
{
    ServerCertificateCustomValidationCallback =
        (httpRequestMessage, cert, cetChain, policyErrors) =>
        {
            return true;
        },
        SslProtocols = SslProtocols.Tls12   |
                       SslProtocols.Tls11   |
                       SslProtocols.Tls     |
                       SslProtocols.Ssl3    |
                       SslProtocols.Ssl2    |
                       SslProtocols.Default |
                       SslProtocols.None
};