I wrote a C# program that uses `HttpWebRequest` to connect to an HTTPS site. The `GetResponse()` method throws an exception:

> 
> SystemError: The underlying connection was closed: Could not establish
>  trust relationship for the SSL/TLS secure channel.
> 
> 
> 

I'm able to connect to the same website using `curl.exe --cacert CAFile.pem`. I'd like to be able use the same trusted CA certificates from the C# program.

How can I get `HttpWebRequest` to use this CA certificate file (or an `X509CertificateCollection` containing certificates parsed from it)?