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I want to wait for a line to be read, but only for so long before timing out. This is what I came up with. Is there a better way to do it?

Dim reader As New System.IO.StreamReader(pipe)

Dim nextCommand = Await New Func(Of Task(Of String))(
    Function()
        Dim t = reader.ReadLineAsync()
        If (Not t.Wait(2000)) Then Throw New MyTimeoutExeption()
        Return t
    End Function).Invoke()
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For operations that don't support cancellation themselves, You can combine Task.WhenAny() with Task.Delay():

Async Function TryAwait(Of T)(target As Task(Of T), delay as Integer) As Task(Of T)
    Dim completed = Await Task.WhenAny(target, Task.Delay(delay))
    If completed Is target Then
        Return Await target
    End If

    Throw New TimeoutException()
End Function

Usage:

Dim nextCommand = Await TryAwait(reader.ReadLineAsync(), 2000)
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  • \$\begingroup\$ Can you please clarify one thing? Return Await target won't actually continue to await, since it's already completed, right? Is its purpose there only to make sure a Task(Of T) is returned? \$\endgroup\$ – rory.ap Jan 28 '15 at 14:11
  • \$\begingroup\$ @roryap Yeah. And also to make sure exceptions from target are propagated. \$\endgroup\$ – svick Jan 28 '15 at 14:21
  • \$\begingroup\$ What about Timeout? \$\endgroup\$ – John Demetriou Jun 4 '18 at 6:36

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