FluentTask.cs

using System;
using System.Collections.Generic;
using System.Threading;

namespace FluentTask
{
	internal class Program
	{
		private static void Main()
		{

			var behaviour = new Behavior()
				.Say("Привет мир!")
				.UntilKeyPressed(b => b
					.Say("Ля-ля-ля!")
					.Say("Тру-лю-лю"))
				.UntilKeyPressed(b => b
					.Say("Aa-a-a-a-aaaaaa!!!")
					.Say("[набирает воздух в легкие]"))
				.Say("Ой!")
				.Delay(TimeSpan.FromSeconds(1))
				.Say("Кто здесь?!")
				.Delay(TimeSpan.FromMilliseconds(2000));

			behaviour.Execute();

		}
	}

	public class Behavior
	{
		private readonly List<Action> actions = new List<Action>();

		public void Execute()
		{
		}

		public Behavior Say(string message)
		{
		}

		public Behavior Delay(TimeSpan timeout)
		{
		}
	}
}