I am doing an SSL3 handshake using an SslStream, but, in spite of my best efforts, the SslStream never sends a client certificate on my behalf. Here is the code:

SSLConnection = new System.Net.Security.SslStream(SSLInOutStream, false, new System.Net.Security.RemoteCertificateValidationCallback(AlwaysValidRemoteCertificate), new System.Net.Security.LocalCertificateSelectionCallback(ChooseLocalCertificate));

X509CertificateCollection CC = new X509CertificateCollection();
CC.Add(Org.BouncyCastle.Security.DotNetUtilities.ToX509Certificate(MyLocalCertificate));

SSLConnection.AuthenticateAsClient("test", CC, System.Security.Authentication.SslProtocols.Ssl3, false);

and then I have AlwaysValidRemoteCertificate just returning true, and ChooseLocalCertificate returning the zeroth element of the array.

The code probably looks a little weird because the project is a little weird, but I think that is beside the point here. The SSL handshake completes. The issue is that instead of sending a certificate message on my behalf (in the handshake process), with the ASN.1 encoded certificate (MyLocalCertificate), the SslStream sends an SSL alert number 41 (no certificate) and then carries on. I know this from packet sniffing. After the handshake is completed, the SslStream marks IsAuthenticated as true, IsMutuallyAuthenticated as false, and its LocalCertificate member is null.

I feel like I'm probably missing something pretty obvious here, so any ideas would be appreciated. I am a novice with SSL, and this project is off the beaten path, so I am kind of at a loss.

P.S. 1: My ChooseLocalCertificate routine is called twice during the handshake, and returns a valid (as far as I can tell), non-null certificate both times.

P.S. 2: SSLInOutStream is my own class, not a NetworkStream. Like I said, though, the handshake proceeds mostly normally, so I doubt this is the culprit... but who knows?