/// <summary>
        /// Observes the events of a given name.
        /// </summary>
        public static IDisposable OfName(
            this IEventStream eventStream,
            string name,
            Action onNext)
        {
            if (onNext == null)
            {
                return(Disposable.Empty);
            }

            return(eventStream
                   .OfName(name)
                   .Subscribe(_ => onNext()));
        }