snippets1-3.vb

Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Threading
Imports System.Threading.Tasks

' How to: Unwrap a Nested Task
Class IntroSnippets

    '<snippet01>
    Shared Function DoWorkAsync() As Task(Of String)

      Return Task(Of String).Run(Function()
                                    '...
                                    Return "Work completed."
                                 End Function)
   End Function

   Shared Sub StartTask()

      Dim t As Task(Of String) = DoWorkAsync()
      t.Wait()
      Console.WriteLine(t.Result)
   End Sub
   '</snippet01>


   Shared Sub Main()

      '<snippet02>
      ' Note the type of t and t2.
      Dim t As Task(Of Task(Of String)) = Task.Run(Function() DoWorkAsync())
      Dim t2 As Task(Of Task(Of String)) = DoWorkAsync().ContinueWith(Function(s) DoMoreWorkAsync())

      ' Outputs: System.Threading.Tasks.Task`1[System.String]
      Console.WriteLine(t.Result)
      '</snippet02>

      '<snippet03>
      ' Unwrap the inner task.
      Dim t3 As Task(Of String) = DoWorkAsync().ContinueWith(Function(s) DoMoreWorkAsync()).Unwrap()

      ' Outputs "More work completed."
      Console.WriteLine(t.Result)
      '</snippet03>


      Console.ReadKey()
   End Sub

   Shared Function DoMoreWorkAsync() As Task(Of String)

      Return Task(Of String).Run(Function()

                                    '...
                                    Return "More work completed."
                                 End Function)
   End Function

End Class