CODEWITHSUNDEEP
parallel-processingtask-parallel-librarytask
Kallol
Kallol

Reputation: 364

2 tasks running in parallel, but one finishes work and waits for the other to complete

This is an extension to the solution in 2 Async tasks in parallel and waiting for results - .Net

The methods of the two tasks are:

Private Sub tempWorker1()
  For i = 1 To 50000
     If i Mod 100 = 0 Then
        Console.WriteLine("From 1:{0}", i)
     End If
  Next
End Sub

Private Sub tempWorker2()
  For i = 1 To 1000
     If i Mod 100 = 0 Then
        Console.WriteLine("From 2:{0}", i)
     End If
  Next
End Sub

The calling methods are:

Dim task1 As Task = Task.Run(AddressOf tempWorker1)
Dim task2 As Task = Task.Run(AddressOf tempWorker2)
Await Task.WhenAll(task1, task2).ConfigureAwait(False)

Now, I'd need to have task1 and task2 run in parallel but task1 should not be over until task2 is complete. And the entire process should wait for both the tasks to complete.

Is there a way to achieve this using TPL. Or do I need to bank on global variables to stop task1 from finishing until task2 sets the global variable?

I am aware of ContinueWith but that would defeat parallelism with the tasks running one after the other - which is not the requirement.

Upvotes: 0

Views: 68

Answers (1)

Stephen Cleary
Stephen Cleary

Reputation: 456917

I'd need to have task1 and task2 run in parallel but task1 should not be over until task2 is complete.

So, just start task2 first, then pass task2 into tempWorker1:

Dim task2 As Task = Task.Run(AddressOf tempWorker2)
Dim task1 As Task = Task.Run(Function() tempWorker1(task2))

And have tempWorker1 call Await task2 when it needs the value.

Upvotes: 1

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