Task-based asynchronous pattern

Basic usage of Async/Await

You can start some slow process in parallel and then collect the results when they are done:

Public Sub Main()
    Dim results = Task.WhenAll(SlowCalculation, AnotherSlowCalculation).Result

    For Each result In results
        Console.WriteLine(result)
    Next
End Sub

Async Function SlowCalculation() As Task(Of Integer)
     Await Task.Delay(2000)

     Return 40
End Function

Async Function AnotherSlowCalculation() As Task(Of Integer)
    Await Task.Delay(2000)

    Return 60
End Function

After two seconds both the results will be available.

Using TAP with LINQ

You can create an IEnumerable of Task by passing AddressOf AsyncMethod to the LINQ Select method and then start and wait all the results with Task.WhenAll

If your method has parameters matching the previous LINQ chain call, they will be automatically mapped.

Public Sub Main()
    Dim tasks = Enumerable.Range(0, 100).Select(AddressOf TurnSlowlyIntegerIntoString)

    Dim resultingStrings = Task.WhenAll(tasks).Result

    For Each value In resultingStrings
        Console.WriteLine(value)
    Next
End Sub

Async Function TurnSlowlyIntegerIntoString(input As Integer) As Task(Of String)
    Await Task.Delay(2000)

    Return input.ToString()
End Function

To map different arguments you can replace AddressOf Method with a lambda:

Function(linqData As Integer) MyNonMatchingMethod(linqData, "Other parameter")