yield 关键字

static void Main(string[] args)
        {
            foreach (var item in Week())
            {
                Console.WriteLine(item);
            }
         
         
        }
        public static IEnumerable Week()
        {
            for (int i = 0; i < 10; i++)
            {
                yield return i;
            }
        }

理解利用了yield关键字之后执行顺序则是foreach一次 Week取得一次，而不是Week一次运行完