Array.ForEach

Consider an array of objects in a VB.NET program. Sometimes we may want to call a subroutine on each object. The Array.ForEach subroutine, with a lambda, can achieve this goal.

With ForEach, we cannot use the result of any functions we call. So we must modify the objects somehow—ForEach does not return a result.

Example

In this example program, we need to have an array of objects on which we can call a method. We introduce the trivial Bird class for the example.

Module Module1

    Class Bird
        Public Sub Add()
            ' Step 3: do something to the Bird class instance in this sub.
            Console.WriteLine("BIRD.ADD")
        End Sub
    End Class

    Sub Main()
        ' Step 1: create an array of objects.
        Dim birds() As Bird = { New Bird(), New Bird(), New Bird() }

        ' Step 2: call Array.ForEach with a Sub to invoke on each element.
        Array.ForEach(birds, Sub(bird as Bird) 
            bird.Add()
        End Sub)
    End Sub

End Module
BIRD.ADD
BIRD.ADD
BIRD.ADD

Sometimes calling a subroutine on each object in an array can be useful. Each object may need to have its internal fields adjusted in response to some sort of external event.