如何等待任务'；结果'；属性具有实际结果
本文关键字：结果 属性 何等待 任务 等待 | 更新日期: 2023-09-27 18:24:21
我有一组任务，收到这些任务后，我使用
Task.Factory.ContinueWhenAll(TasksList.ToArray(), CompleteTasks);
其中CompleteTasks（）是我在所有任务都应该完成计算结果后使用的方法。这是第一次，但当我再次浏览它时，一些Tasks results属性显示"尚未计算"，它仍然会浏览我的CompleteTasks方法。处理这个问题的最佳方法是什么？
以下是完整的代码：
public Checker(IEnumerable<Website> websites)
{
WebsiteHelper.Websites = websites.ToList<Website>();
Check(WebsiteHelper.Websites);
}
public void Check(IList<Website> tempWeb)
{
int mySiteCounter = 0;
// Go through each website in the list in parallel
Parallel.ForEach(tempWeb, web =>
{
TempWebResult.Add(new WebsiteResult { });
try
{
StartingTime = DateTime.Now;
PageCheck(web, mySiteCounter++);
EndingTime = DateTime.Now;
}
//write the Message to a log
//Catch Exceptions
});
CheckNewResult();
}
public void PageCheck(Website webParam, int mySiteCounter)
{
TempCounter = mySiteCounter;
TempURL = webParam.SiteUrl;
Uri uri = new Uri(TempURL);
HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(uri);
myReq.Method = WebRequestMethods.Http.Get; // Used to contact the Internet resource
try
{
myReq.KeepAlive = false;
myReq.Timeout = 5 * 60 * 1000; //set to 10 minutes
var checkResult = TempWebResult.ElementAt(mySiteCounter);
//Use .FromAsync to start asynchronous operation request and to return the actual web response
try
{
checkResult.RequestSentTime = DateTime.Now;
Stopwatch WatchTimer = Stopwatch.StartNew();
Task<WebResponse> task = Task<WebResponse>.Factory.FromAsync(
myReq.BeginGetResponse,
myReq.EndGetResponse,
null);
//Add a task to the task list
TempTasksList.Add(task);
Console.WriteLine(mySiteCounter + ": Url to check: " + myReq.RequestUri);
//Continue after request and response have been made
task.ContinueWith(t =>
{
var responseCode = (HttpWebResponse)t.Result;
WatchTimer.Stop();
checkResult.milli = WatchTimer.ElapsedMilliseconds;
checkResult.ResponseReceivedTime = DateTime.Now;
//diff = checkResult.ResponseReceivedTime - checkResult.RequestSentTime;
//checkResult.milli = (int)diff.TotalMilliseconds;
checkResult.Url = webParam.SiteUrl;
checkResult.SystemStatus = "Up";
webParam.SiteStatus = checkResult.SystemStatus;
checkResult.SystemId = mySiteCounter + "-" + myReq.RequestUri.ToString();
Console.WriteLine(mySiteCounter + "Url that came back: " + responseCode.ResponseUri);
ReadStreamFromResponse(t.Result);
if (responseCode.StatusCode == HttpStatusCode.OK) // Checks if status is OK or not
{
checkResult.ResponseStatus = responseCode.StatusCode.ToString();
checkResult.ResponseStatusCode = "Up";
checkResult.SystemStatus = "Up";
webParam.SiteStatus = checkResult.SystemStatus;
checkResult.StatusFlag = true;
//Return the Response Url
checkResult.ResponseUrl = responseCode.ResponseUri.ToString();
}
if (checkResult.SystemName == null)
checkResult.SystemName = "";
if (checkResult.Message == null)
checkResult.Message = "";
if (checkResult.ResponseUrl == null)
checkResult.ResponseUrl = "";
});
task.ContinueWith((t) =>
{
WatchTimer.Stop();
checkResult.milli = WatchTimer.ElapsedMilliseconds;
ErrorMessage = GetException(t.Exception);
checkResult.ResponseReceivedTime = DateTime.Now;
// diff = checkResult.ResponseReceivedTime - checkResult.RequestSentTime;
// checkResult.milli = (int)diff.TotalMilliseconds;
Console.WriteLine("Status Not Ok");
checkResult.SystemId = mySiteCounter + "-" + myReq.RequestUri.ToString();
checkResult.ResponseStatus = ErrorMessage;
checkResult.ResponseStatusCode = "Down";
checkResult.SystemStatus = "Down";
webParam.SiteStatus = checkResult.SystemStatus;
checkResult.StatusFlag = false;
},
TaskContinuationOptions.OnlyOnFaulted);
}
//Exceptions caught
}
//Exceptions caught
}
/// <summary>
/// This method converts the TasksList into an array
/// and calls the Complete Tasks method
/// </summary>
private void CheckNewResult()
{
Task.Factory.ContinueWhenAll(TempTasksList.ToArray(), CompleteTasks);
}
/// <summary>
/// This method waits until all tasks have ran to
/// completion so it can print results
/// </summary>
/// <param name="tasks"> Array of completed tasks</param>
private void CompleteTasks(Task[] tasks)
{
WebsiteHelper.myLog.Info("***********************************************************");
WebsiteHelper.myLog.Info("ready to print check results now");
//Wait until all tasks have ran to completion
if (tasks.Any(t => t.Status == (TaskStatus.RanToCompletion) || t.Status == (TaskStatus.Faulted)))
{
Parallel.ForEach(TempWebResult, result =>
{
//Console.WriteLine(result);
// Console.WriteLine("new line");
WebsiteHelper.myLog.Info(result.SQL);
});
}
if(DownSitesHandler.FirstTime == true)
{
DownSitesHandler.FirstTime = false;
CheckDownSites();
if (WebsiteHelper.Self().HasDownSite == true)
ReCheck();
}
Console.WriteLine("done printing all results");
}
/// <summary>
/// This method rechecks all down websites
/// </summary>
public void ReCheck()
{
//Checker newCheckerObject = new Checker(downsites);
WebsiteHelper.myLog.Info(DateTime.Now + " -- Begin to re-check down sites ");
IList<Website> temporaryWebList = DownSitesHandler.downsites.ToList<Website>();
Check(temporaryWebList);
//newCheckerObject.SendRequest();
}
我没有仔细梳理您的所有代码，但您似乎没有正确使用continuation。延续本身就是一项单独的任务，在某个时刻，您也需要等待它完成。例如：
var first = Task.Run(() => { Console.Write("First"); });
var second = first.ContinueWith(t => Console.WriteLine("Second"));
second.Wait();
如果你只等待"第一个"，就不能保证延续已经结束。ContinueWhenAll方法也是如此，它返回您需要等待的任务。
此外，向同一任务添加多个延续并不意味着两者之间存在任何优先级关系。在先行任务完成后，它们可以按任何顺序启动、并行运行或其他任何方式。例如：
var taskA = Task.Run(() => { Console.Write("A"); });
var taskB1 = taskA.ContinueWith(t => Console.WriteLine("B1"));
var taskB2 = taskA.ContinueWith(t => Console.WriteLine("B2"));
var bothFinished = Task.WhenAll(taskB1, taskB2);
bothFinished.Wait();
在这里，你可能会看到B1和B2以任何顺序打印，如果你想确保它们已经运行，你需要等待两者完成。
这可能是也可能不是你所有问题的解决方案，但它应该是开始。
发生的情况是您的任务尚未完成其工作。
解决方案1：使用Task.WaitAll(tasks);这将等待所有剩余任务结束；
解决方案2：使用类似的东西：
var continuation = Task.Factory.ContinueWhenAll(
tasks,
(antecedents) =>
{
//Do Some Work Here
});
continuation.Wait();
希望能有所帮助。
我能够处理这个问题。在重新检查之前，我调用了Thread.Sleep方法，让系统有时间完成，这样可以顺利地得到所有结果。