public void OnNextElement(Maybe <LambdaExecution <TContext> > func) => _onNextElement = _onNextElement.Combine(func);
public void OnFinish(Maybe <LambdaFinish <TContext> > func) => _onFinish = _onFinish.Combine(func);
public void OnExecute(Maybe <LambdaExecution <TContext> > func) => _onExecute = _onExecute.Combine(func);