我試圖創建將運行異步方法的任務,問題是,我不能await
的Action
參數在任務的構造函數,或Task.Factory.StartNew
的參數。C#啓動任務運行異步方法
根據我如何實例化我的任務,我有不同的問題。我已經提供了七個例子,並對各自在下面創建的問題發表了評論
示例代碼:(任務創建的7個例子)
private ConcurrentDictionary<int, Task> Tasks { get; set; }
private bool active = true;
private async Task StartTasks()
{
int numTasks = 5;
for(int i = 0; i < numTasks; i++)
{
//Task status is almost instantly "RanTocompletion" while work is still being done
Task task = new Task<Task>(DoWork, "someinfo", TaskCreationOptions.LongRunning);
task.Start();
//Cannot await method group
Task task = new Task(await DoWork, "someinfo", TaskCreationOptions.LongRunning);
task.Start();
//Task status is almost instantly "RanTocompletion" while work is still being done
Task task = new Task(async (object state) => await DoWork(state), "someinfo", TaskCreationOptions.LongRunning);
task.Start();
//Throws a "Start may not be called on a promise-style task." Exception
Task task = new Task<Task>(DoWork, "someinfo", TaskCreationOptions.LongRunning).Unwrap();
task.Start();
//Task starts doing work after Start() is called, then throws a "Start may not be called on a promise-style task." Exception
Task task = new Task(DoWork, "someinfo", TaskCreationOptions.LongRunning);
task.Start();
//Task starts doing work, but status is "WaitingForActivation
Task task = Task.Factory.StartNew(DoWork, "someinfo", TaskCreationOptions.LongRunning);
//Throws a "Start may not be called on a promise-style task." Exception
Task task = Task.Factory.StartNew(DoWork, "someinfo", TaskCreationOptions.LongRunning).Unwrap();
//For checking up on tasks as work is done
Tasks.TryAdd(task.Id, Task);
}
}
private async Task DoWork(object state)
{
while (active)
{
await MakeHttpRequest();
await DoSomethingCpuBound();
//..etc
}
//do any cleanup and return
}
我不能使用Task.Run()
,因爲不提供TaskCreationOptions
。這些任務將在字面上運行。
如何啓動任務以等待異步操作?
這聽起來像是一個X-Y問題。你試圖解決X,你認爲Y是答案,但是你不知道如何去做Y,所以你在問這個問題。相反,你最好問問X.你應該告訴我們X是什麼。 – Enigmativity
作爲最後的手段,您可以創建'Task.Factory.StartNew'的同步匿名委託,並通過'.GetAwaiter()。GetResult()'等待。 – zerkms
@Enigmativity我正在使用'HttpClient'從我正在抓取的網站上下載頁面。由於延遲時間很長,我可以將更多的頁面並行拖到更好的頁面上。這有效,但我希望能夠看到任務狀態。當運行這個非異步線程在等待'HttpClient'時被阻塞。我試圖解決這個問題 –