//Using Composition and IoC to add a logging to the IService implementation without violating OCP.
//Instantiate with: For<IService>.Use<LoggingService>().Ctor<IService>().Is<SomeService>();
//
//create a LoggingService : IService that takes the *real* IService in it's c'tor
public class LoggingService : IService
{
    private IService _realService;
    private ILogger _log;

    public LoggingService(IService realService, ILogger log)
    {
        _realService = realService;
        _log = log;
    }

    public void DoStuff()
    {
        _log.Log("Doing some stuff");
        _realService.DoStuff();
    }
}