Question

如果你有

Private Shared Sub msg(Optional message As String = "")
    Debug.WriteLine(Threading.Thread.CurrentThread.ManagedThreadId & " " & message)
End Sub
<TestMethod()>
Public Sub TestMethod1()
    Dim cancel As New Threading.CancellationTokenSource
    msg("starting")
    Dim start As DateTime = DateTime.Now
    Dim task As New Task(Sub()
                             msg("in thread")
                             Do Until Now.Subtract(start).TotalMilliseconds > 2000
                                 Threading.Thread.Sleep(500)
                                 msg("loop")
                                 cancel.Token.ThrowIfCancellationRequested()
                             Loop
                         End Sub, cancel.Token, TaskCreationOptions.LongRunning)
    task.ContinueWith(Sub(result As task)
                          msg("Continue task running")
                          Debug.WriteLine(result.Status.ToString & If(result.Exception Is Nothing, ", no exception", ", exception occurred " & result.Exception.GetType.Name))
                          Do Until Now.Subtract(start).TotalMilliseconds > 10000
                              cancel.Token.ThrowIfCancellationRequested()
                              Threading.Thread.Sleep(500)
                              msg("innerloop")
                          Loop
                      End Sub)
    task.Start()
    Try
        If Not task.Wait(4000, cancel.Token) Then
            msg("wait expired, time to cancel)")
            cancel.Cancel()
        End If
        task.Wait()

    Catch ex As OperationCanceledException
        msg("task was cancelled")
    Finally
        msg("finishing")
    End Try
End Sub

问题是当我执行task.Wait（4000，cancel.Token）时，这应该最终失败，因为ContinueWith任务在超时内不会完成。

似乎等待只适用于任务并且不考虑链条，我怎么能让它等到链条＆＃34;完了吗？

Answer 1

等待ContinueWith函数返回的任务。

Task.Wait（）不包含任何链接（ContinueWith）任务

1 个答案: