class Program
    {
        static void Main(string[] args)
        {
            ProcessTaskAsync();

            Console.ReadLine();
        }

        /// <summary>
        /// 等待并输出
        /// </summary>
        /// <param name="second"></param>
        /// <returns></returns>
        static async Task<int> DelayAsync(int second)
        {
            await Task.Delay(TimeSpan.FromSeconds(second));
            return second;
        }

        static async Task ProcessTaskAsync()
        {
            //创建任务队列
            Task<int> task1 = DelayAsync(2);
            Task<int> task2 = DelayAsync(3);
            Task<int> task3 = DelayAsync(1);

            var tasks = new[] { task1, task2, task3 };

            var processTasks = tasks.Select(async t =>
              {
                  var result = await t;
                  Console.WriteLine(result);
              });

            //等待全部任务完成
            await Task.WhenAll(processTasks);
        }
    }