Question

我正在发送大量的客户端get请求，并且以下代码可以正常工作，但是一旦找到StatusCode.OK的HttpResponseMessage后，如何强制执行停止，然后返回该单个Task。

  public List<Task<HttpResponseMessage>> GetUploadURLAsync(List<string> list)
        {
            List<Task<HttpResponseMessage>> tasks = new List<Task<HttpResponseMessage>>();
            using (HttpClient client = new HttpClient())
            {
                for(int i = 0; i < list.Count; i++)
                {
                  <client get async code generating task list>
                }
                Task.WaitAll(tasks.ToArray());
            }
            return tasks;
    }

Answer 1

类似这样的东西：

class SomeClass
{
    private static HttpClient _httpClient = new HttpClient();

    public static Task<HttpResponseMessage> GetFirstSuccessAsync(List<string> list)
    {
        var tasks = new List<Task<HttpResponseMessage>>();
        foreach (var url in list) {
            tasks.Add(_httpClient.GetAsync(url));
        }

        return WhenAnySuccess(tasks);
    }

    private static async Task<HttpResponseMessage> WhenAnySuccess(List<Task<HttpResponseMessage>> tasks)
    {
        while (tasks.Count > 0) {
            Task<HttpResponseMessage> task = await Task.WhenAny(tasks);
            if (task.Status == TaskStatus.RanToCompletion && task.Result.StatusCode == HttpStatusCode.OK) {
                return task.Result;
            }

            tasks.Remove(task);
        }

        return null;
    }
}

class Program
{
    static void Main(string[] args)
    {
        var response = SomeClass.GetFirstSuccess(new List<string> { "http://google.com", "http://microsoft.com" }).Result;
        Console.WriteLine(response.RequestMessage.RequestUri);
        Console.ReadKey();
    }
}

Answer 2

假设您的异步操作支持取消操作，则需要CancellationTokenSource。

如果满足条件，如何停止运行任务列表

2 个答案: