在一定时间后取消 Task.WhenAll

Question

我有一个异步操作，它将航空公司列表作为参数并返回一些数据，并且我有一个航空公司列表，我想为其获取数据。

但是，如果在预定义的时间后我无法获得所有这些航空公司的数据，我想停止等待并将其他内容返回给用户。

public async Task Run()
{
    var watch = System.Diagnostics.Stopwatch.StartNew();
    await RunAirline();
    watch.Stop();
    Console.WriteLine($"Total Execution Time: {watch.ElapsedMilliseconds + Environment.NewLine}");
    //return $"Total Execution Time: {watch.ElapsedMilliseconds + Environment.NewLine}";
    //Console.ReadLine();
}

private static async Task RunAirline()
{
    try
    {
        List<string> AirlineList = GetAirLineCodes();
        List<Task<WebsiteDataModel.WebsiteDataModel>> taskList = new List<Task<WebsiteDataModel.WebsiteDataModel>>();
        foreach (string AirlineCode in AirlineList)
        {
            taskList.Add(Task.Run(() => CallindividualAirline(AirlineCode)));

        }
        var result = await Task.WhenAll(taskList);
        foreach (WebsiteDataModel.WebsiteDataModel model in result)
        {
            Display(model);
        }
    }
    catch (Exception Ex)
    {
        Console.WriteLine(Ex.Message.ToString());
    }
}

private static List<string> GetAirLineCodes()
{
    return new List<string>() 
    {
        "A",
        "B",
        "C"
    };
}

private static void Display(WebsiteDataModel.WebsiteDataModel result)
{
    Console.WriteLine($"Website Content as {result.DataContent} , Website Name as :  {result.WebsiteName} Status as : {result.Status} , Content length as : {result.WebsiteData.Length} ----- Error as  : {result.error.FaultException.ToString()}." + Environment.NewLine);
}

private static WebsiteDataModel.WebsiteDataModel CallindividualAirline(string AirlineCode)
{
    WebsiteDataModel.WebsiteDataModel LobjWebsiteDataModel = new WebsiteDataModel.WebsiteDataModel();
    WebsiteDataModel.ErrorData LobjErrorData = new WebsiteDataModel.ErrorData();
    try
    {
        switch (AirlineCode)
        {
            // calling Airline API...........
            case "A":
                ClsAirOne LobjAirOne = new ClsAirOne();
                LobjWebsiteDataModel = LobjAirOne.GetAirDataData("https://book.xxxxx.com");
                return LobjWebsiteDataModel;
            case "B":
                ClsAirTwo LobjAirTwo = new ClsAirTwo();
                LobjWebsiteDataModel = LobjAirTwo.GetAirData("https://book.xxxxx.in");
                return LobjWebsiteDataModel;
            case "C":
                ClsAirThree LobjAirThree = new ClsAirThree();
                LobjWebsiteDataModel = LobjAirThree.GetAirData("https://xxxxx.in/");
                return LobjWebsiteDataModel;

            default:
                return LobjWebsiteDataModel;
        }


    }
    catch (Exception Ex)
    {

        LobjWebsiteDataModel.Status = "0";
        LobjWebsiteDataModel.WebsiteData = "";
        LobjErrorData.FaultException = "ERR-01" + Ex.Message.ToString();
        LobjWebsiteDataModel.error = LobjErrorData;
        return LobjWebsiteDataModel;
    }
}

Answer 1

执行此操作的最佳方法是取消传递给Task.WhenAll 的每个操作。您可以创建一个带有超时的取消令牌源，然后将其 CancellationToken 传递给实际执行 I/O 的方法。

例如：

public async Task Run()
{
  ...
  using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
  await RunAirline(cts.Token);
  ...
}

private static async Task RunAirline(CancellationToken cancellationToken)
{
  ...
  foreach (string AirlineCode in AirlineList)
    taskList.Add(Task.Run(() => CallindividualAirline(AirlineCode, cancellationToken)));
  ...
}

private static WebsiteDataModel.WebsiteDataModel CallindividualAirline(string AirlineCode, CancellationToken cancellationToken)
{
  ...
  ClsAirOne LobjAirOne = new ClsAirOne();
  LobjWebsiteDataModel = LobjAirOne.GetAirDataData("https://book.xxxxx.com", cancellationToken);
  ...
  ClsAirTwo LobjAirTwo = new ClsAirTwo();
  LobjWebsiteDataModel = LobjAirTwo.GetAirData("https://book.xxxxx.in", cancellationToken);
  ...
}