C#异步编程（二）：异步基础补充

这次来介绍一些用法：

await一批任务，不等候其它任务完成，直接执行后续的任务。

    class Program
    {
        static void Main(string[] args)
        {
            var taskA = DelayAndRerutnAsync(2);
            var taskB = DelayAndRerutnAsync(3);
            var taskC = DelayAndRerutnAsync(1);
            var tasks = new[] {taskA, taskB, taskC};
            var processingTasks= (from t in tasks select AwaitAndProcessAsync(t)).ToArray();
            Task.WhenAll(processingTasks);
            Console.Read();
        }

        static async Task<int> DelayAndRerutnAsync(int val)
        {
            await Task.Delay(TimeSpan.FromSeconds(val));
            Console.WriteLine("等候了{0}",val);
            return val;
        }

        static async Task AwaitAndProcessAsync(Task<int> task)
        {
            var result = await task;
            Console.WriteLine(result);
        }
    }

从打印出的结果可以看到，在等候1秒的方法执行完成后并没有等待其它方法的执行，而是直接执行后面的异步方法。

下面介绍一种使用匿名方法的写法

    class Program
    {
        static void Main(string[] args)
        {
            var taskA = DelayAndRerutnAsync(2);
            var taskB = DelayAndRerutnAsync(3);
            var taskC = DelayAndRerutnAsync(1);
            var tasks = new[] {taskA, taskB, taskC};
            var processingTasks = tasks.Select(async task =>
            {
                var result = await task;
                Console.WriteLine(result);
            });
            Task.WhenAll(processingTasks);
            Console.Read();
        }

        static async Task<int> DelayAndRerutnAsync(int val)
        {
            await Task.Delay(TimeSpan.FromSeconds(val));
            Console.WriteLine("等候了{0}",val);
            return val;
        }

        
    }