The IRequest::get_ClientCertificate method retrieves the ClientCertificate collection of the Request object.
HRESULT get_ClientCertificate(
IRequestDictionary ** ppDictReturn // pointer to an
// IRequestDictionary interface
// pointer that receives the ClientCertificate collection
);
You can iterate through the ClientCertificate collection with the get__NewEnum method exposed by the IRequestDictionary interface. You can also retrieve a specific ClientCertificate value with the get_Item method.