异步超时后直接返回

应用场景

     异步同时请求多个地址，获得返回的信息并输出，排除时间响应太久的以免造成不必要的时间等待。

   

  class Program
    {
        static void Main(string[] args)
        {
            TaskTest();
            Console.ReadLine();
        }

        static async void ddd()
        {
            Stopwatch sw = new Stopwatch();
            sw.Start();
            List<string> urls = new List<string>() { "http://www.baidu.com", "http://www.360.com" };
            string a = await DownloadAllAsync(urls);

            Console.WriteLine(a);
            sw.Stop();
            Console.WriteLine(sw.ElapsedMilliseconds);
            Console.ReadLine();
        }
        static HttpClient httpClient = new HttpClient();
        static async Task<string> DownloadAllAsync(IEnumerable<string> urls)
        {

            var downloads = urls.Select(url => httpClient.GetStringAsync(url));
            Task<string>[] downloadTasks = downloads.ToArray();

            string[] pages = await Task.WhenAll(downloadTasks);

            return string.Concat(pages);
        }

        static void TaskTest()
        {
            var cts = new CancellationTokenSource(TimeSpan.FromMilliseconds(2000));
            Task<string> t1 = GetString("http://www.baidu.com");
            Task<string> t2 = GetString("http://www.360.com");
            Task<string> t3 = GetString("http://www.github.com");
           
            Task<string>[] arr = new Task<string>[] { t1, t2, t3 };
            Task.WaitAll(arr,2000);
            foreach (var dd in arr)
                Console.WriteLine(dd.Result.ToString());
        }

        static async Task<string> GetString(string str)
        {
            return await httpClient.GetStringAsync(str);

        }

源码