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;
}

}