异步超时后直接返回

Posted 2020-08-01 清风神剑

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。

   

 1   class Program
 2     {
 3         static void Main(string[] args)
 4         {
 5             TaskTest();
 6             Console.ReadLine();
 7         }
 8 
 9         static async void ddd()
10         {
11             Stopwatch sw = new Stopwatch();
12             sw.Start();
13             List<string> urls = new List<string>() { "http://www.baidu.com", "http://www.360.com" };
14             string a = await DownloadAllAsync(urls);
15 
16             Console.WriteLine(a);
17             sw.Stop();
18             Console.WriteLine(sw.ElapsedMilliseconds);
19             Console.ReadLine();
20         }
21         static HttpClient httpClient = new HttpClient();
22         static async Task<string> DownloadAllAsync(IEnumerable<string> urls)
23         {
24 
25             var downloads = urls.Select(url => httpClient.GetStringAsync(url));
26             Task<string>[] downloadTasks = downloads.ToArray();
27 
28             string[] pages = await Task.WhenAll(downloadTasks);
29 
30             return string.Concat(pages);
31         }
32 
33         static void TaskTest()
34         {
35             var cts = new CancellationTokenSource(TimeSpan.FromMilliseconds(2000));
36             Task<string> t1 = GetString("http://www.baidu.com");
37             Task<string> t2 = GetString("http://www.360.com");
38             Task<string> t3 = GetString("http://www.github.com");
39            
40             Task<string>[] arr = new Task<string>[] { t1, t2, t3 };
41             Task.WaitAll(arr,2000);
42             foreach (var dd in arr)
43                 Console.WriteLine(dd.Result.ToString());
44         }
45 
46         static async Task<string> GetString(string str)
47         {
48             return await httpClient.GetStringAsync(str);
49 
50         }

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源码