public interface ICustomerRepository
{
	Customer RetrieveById(string id);
}

public class CustomerSessionCacheRepository(ICustomerRepository innerRepository) : ICustomerRepository
{
	public Customer RetrieveById(string id)
	{
		if (_cache.Contains(id))
			return _cache[id];
		else
		{
			var data = innerRepository.RetrieveById(id);
			_cache[id] = data;
			return data;
		}
	}
}


public class CustomerSessionCacheRepository()
{
	public Customer RetrieveById(string id)
	{
		// NHibernate Magic to get the record...
	}
}