public void Process(Changestep <TData> step)
        {
            switch (step.Operation)
            {
            case CrudOperation.Create:
                Target.OnCreate(step);
                break;

            case CrudOperation.Update:
                Target.OnUpdate(step);
                break;

            case CrudOperation.Delete:
                Target.OnDelete(step);
                break;
            }
        }
 void ICrudObserver <TData> .OnDelete(Changestep <TData> step)
 {
     Buffer.Add(step);
 }