Imports System.ComponentModel
 
Public Class MVC_Controller
    Private clients As New ArrayList
 
    Public Delegate Sub OnAddingHandler(ByVal sender As MVC_Controller, ByVal _
      cl As Client, ByRef cancel As Boolean)
    Public Delegate Sub OnChangeHandler(ByVal sender As MVC_Controller, ByVal _
    cl As Client)
    Public Delegate Sub OnRemoveHandler(ByVal sender As MVC_Controller, ByVal _
    cl As Client)
 
    Public Event OnAdding As OnAddingHandler
    Public Event OnChange As OnChangeHandler
    Public Event OnRemove As OnRemoveHandler
 
    Public Function IndexOf(ByVal cl As Client) As Integer
        Return clients.IndexOf(cl)
    End Function
 
    Public Sub add(ByVal cl As Client)
        Dim CancelIt As Boolean = False
        Dim handler As OnAddingHandler = OnAddingEvent
        If (handler IsNot Nothing) Then
            ' Hier ein paar tricks. Du kannst mehr als einen Handler 
            ' installieren, also
            ' müssen wir bei jedem überprüfen, ob wir Invoken müssen
            For Each singleCast As OnAddingHandler In handler.GetInvocationList( _
              )
                Dim syncInvoke As ISynchronizeInvoke = TryCast( _
                singleCast.Target, ISynchronizeInvoke)
                Try
                    If ((syncInvoke IsNot Nothing) AndAlso ( _
                      syncInvoke.InvokeRequired)) Then
                        syncInvoke.Invoke(singleCast, New Object() {Me, cl, _
                        CancelIt})
                    Else
                        singleCast(Me, cl, CancelIt)
                    End If
                Catch ex As Exception
                End Try
            Next
        End If
        If CancelIt = False Then
            clients.Add(cl)
            'Und hier hängen wir uns in das onChangeEvent des Clients ein
            AddHandler cl.OnChanged, AddressOf ClientChanged
            AddHandler cl.OnRemoved, AddressOf ClientRemoved
        End If
    End Sub
 
    Private Sub ClientChanged(ByVal cl As Client)
        Dim handler As OnChangeHandler = OnChangeEvent
        If (handler IsNot Nothing) Then
            For Each singleCast As OnChangeHandler In handler.GetInvocationList( _
              )
                Dim syncInvoke As ISynchronizeInvoke = TryCast( _
                singleCast.Target, ISynchronizeInvoke)
                Try
                    If ((syncInvoke IsNot Nothing) AndAlso ( _
                      syncInvoke.InvokeRequired)) Then
                        syncInvoke.Invoke(singleCast, New Object() {Me, cl})
                    Else
                        singleCast(Me, cl)
                    End If
                Catch ex As Exception
                End Try
            Next
        End If
    End Sub
 
    Private Sub ClientRemoved(ByVal cl As Client)
        Dim handler As OnRemoveHandler = OnRemoveEvent
        If (handler IsNot Nothing) Then
            For Each singleCast As OnRemoveHandler In handler.GetInvocationList( _
              )
                Dim syncInvoke As ISynchronizeInvoke = TryCast( _
                singleCast.Target, ISynchronizeInvoke)
                Try
                    If ((syncInvoke IsNot Nothing) AndAlso ( _
                      syncInvoke.InvokeRequired)) Then
                        syncInvoke.Invoke(singleCast, New Object() {Me, cl})
                    Else
                        singleCast(Me, cl)
                    End If
                Catch ex As Exception
                End Try
            Next
        End If
    End Sub
End Class