Public MustInherit Class DataGatherer
 
    Public Event ItemGathered(sender As Object, obj As DataObject)
 
    Public MustOverride Sub Start()
 
    Protected Friend Sub OnItemGathered(obj As DataObject)
        RaiseEvent ItemGathered(Me, obj)
    End Sub
 
    Protected Friend Sub Wait(milliseconds As Integer)
        Dim watch As New Stopwatch
        watch.Restart()
 
        While watch.ElapsedMilliseconds < milliseconds
        End While
    End Sub
 
End Class
 
Public Class DataGathererA
    Inherits DataGatherer
 
    Public Overrides Sub Start()
        For i As Integer = 0 To 100
            Dim data As New DataObject("Aufgabe A", i.ToString)
 
            Call OnItemGathered(data)
            Call Wait(1000)
        Next
    End Sub
 
End Class

Public Class DataController
 
    Private pItems As New System.ComponentModel.BindingList(Of DataObject)
    Private operation As AsyncOperation
 
    Public ReadOnly Property Items() As System.ComponentModel.BindingList(Of _
      DataObject)
        Get
            Return pItems
        End Get
    End Property
 
    Public Sub Start(gathererTask As DataGatherer)
        AddHandler gathererTask.ItemGathered, AddressOf Gatherer_ItemGathered
 
        Dim t As Task = Task.Factory.StartNew(New Action(AddressOf _
          gathererTask.Start))
    End Sub
 
    Private Sub Gatherer_ItemGathered(sender As System.Object, e As DataObject)
        'Me.Items.Add(e)
        operation = AsyncOperationManager.CreateOperation(Nothing)
        operation.Post(New SendOrPostCallback(AddressOf AddItem), e)
        operation.OperationCompleted()
    End Sub
 
    Private Sub AddItem(data As Object)
        If TypeOf data Is DataObject Then
            Me.Items.Add(DirectCast(data, DataObject)) ' *
        End If
    End Sub
End Class