private void OnUndo(SampleState state, StorageObject storage)
        {
            var lastValue = state.HelloString;

            state.HelloString = (string)storage.Get("hello");
            storage.Set("hello", lastValue);
        }
 private void OnNext(SampleState state, StorageObject storage)
 {
     state.HelloString = "Hello Universe!";
     storage.Set("hello", state.HelloString);
 }
 private void OnInvoke(SampleState state, StorageObject storage)
 {
     state.HelloString = "Hello World!";
     storage.Set("hello", state.HelloString);
 }