Public Class Form1
 
    Public Structure Pupil
 
        Private myName As String
        Private myId As Integer
 
        Property ID() As Integer
            Get
                Return myId
            End Get
            Set(ByVal value As Integer)
                myId = value
            End Set
        End Property
 
        Property Name() As String
            Get
                Return myName
            End Get
            Set(ByVal value As String)
                myName = value
            End Set
        End Property
 
        Public Sub ChangeName(ByVal newname As String)
 
            myName = newname
 
        End Sub
 
        Public Sub New(ByVal Name As String, ByVal ID As Integer)
 
            myName = Name
            myId = ID
 
        End Sub
 
    End Structure
 
    Public Structure Seminar
 
        Public myPupils As List(Of Pupil)
        Private myID As Integer
        Private myName As String
        Private CurrPupID As Integer
 
        Public Sub New(ByVal Name As String, ByVal ID As Integer)
 
            myPupils = New List(Of Pupil)
            myName = Name
            myID = ID
            CurrPupID = 0
 
        End Sub
 
        Public Sub AddPupil(ByVal Name As String)
 
            Dim NewPupil As New Pupil(Name, CurrPupID)
 
            myPupils.Add(NewPupil)
            CurrPupID += 1
 
        End Sub
 
        Public Sub ChangeName(ByVal NewName As String)
 
            myName = NewName
 
        End Sub
 
        Public Function GetPupilByID(ByVal SearchID As Integer) As Pupil
 
            Dim result As New Pupil("", -1)
 
            For Each CurrPup As Pupil In myPupils
 
                If CurrPup.ID = SearchID Then Return CurrPup : Exit Function
 
            Next
 
            Return result
 
        End Function
 
        Public Property ID() As Integer
            Get
                Return myID
            End Get
            Set(ByVal value As Integer)
                myID = value
            End Set
        End Property
 
        Public Property Name() As String
            Get
                Return myName
            End Get
            Set(ByVal value As String)
                myName = value
            End Set
        End Property
 
    End Structure
 
    Public Structure SchoolHandler
 
        Private mySeminars As List(Of Seminar)
        Private currSemID As Integer
 
        Public Sub New(ByVal StartID As Integer)
 
            mySeminars = New List(Of Seminar)
            currSemID = StartID
 
        End Sub
 
        Public Sub Add(ByVal Name As String)
 
            Dim NewSem As New Seminar(Name, currSemID)
 
            mySeminars.Add(NewSem)
            currSemID += 1
 
        End Sub
 
        Public Function GetSeminarByID(ByVal SearchID As Integer) As Seminar
 
            Dim result As New Seminar
            result.ID = -1
 
            For Each CurrSem As Seminar In mySeminars
 
                If CurrSem.ID = SearchID Then Return CurrSem : Exit Function
 
            Next
 
            Return result
 
        End Function
 
        Public Sub ShowAllPupils()
 
            For Each CurrSem As Seminar In mySeminars
 
                Debug.Print(CurrSem.Name)
 
                For Each CurrPup As Pupil In CurrSem.myPupils
 
                    Debug.Print(CurrPup.Name)
 
                Next
 
                Debug.Print(vbNewLine)
 
            Next
 
 
        End Sub
 
    End Structure
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
 
        Dim school As New SchoolHandler(1)
 
        school.Add("Mathe")
        school.Add("Deutsch")
 
        school.GetSeminarByID(1).AddPupil("Hans")
        school.GetSeminarByID(2).AddPupil("Bernd")
 
        school.ShowAllPupils()
 
        school.GetSeminarByID(1).GetPupilByID(1).ChangeName("Georg")
        school.GetSeminarByID(1).ChangeName("Sport")
 
        school.ShowAllPupils()
 
    End Sub
 
End Class
 
Hier die noch erzeugte Ausgabe:
 
Mathe
Hans
 
Deutsch
Bernd
 
Mathe
Hans
 
Deutsch
Bernd
 
Die gewünschte Ausgabe wäre:
 
Mathe
Hans
 
Deutsch
Bernd
 
Sport      <-
Georg      <-
 
Deutsch
Bernd