Public Class frmSummationDemo
 
    'Dataset, Tabellen, Relation     
    Dim ds As New DataSet
 
    Dim dtparent As New DataTable("Parent")
 
    Dim WithEvents dtchild As New DataTable("Child")
 
    Dim rel As DataRelation
 
 
    'Datagridviews
    Dim dgvParent As New DataGridView With _
        {.Parent = Me, .Width = 200}
 
    Dim dgvChild As New DataGridView With _
        {.Parent = Me, .Width = 200, .Left = 210}
 
 
 
    Private Sub frmSummationDemo_Load(sender As System.Object, _
        e As System.EventArgs) Handles MyBase.Load
 
        'Füllen des Dataset mit Testspalten und einer Relation
        With dtparent
            .Columns.Add("SatzID", GetType(Integer))
            .Columns.Add("Summe", GetType(Integer))
            .PrimaryKey = New DataColumn() {.Columns("SatzID")}
 
            .Rows.Add(1, 0)
            .Rows.Add(2, 0)
            .Rows.Add(3, 0)
        End With
 
 
        With dtchild
            .Columns.Add("SatzID", GetType(Integer))
            .Columns("SatzID").DefaultValue = 1
            .Columns.Add("Menge", GetType(Double))
            .Columns("Menge").DefaultValue = 0
        End With
 
        With ds
            .Tables.Add(dtparent) : .Tables.Add(dtchild)
 
            'Erstellung der Relation 
            .Relations.Add(New DataRelation("SatzID", _
            dtparent.Columns("SatzID"), dtchild.Columns("SatzID")))
        End With
 
        'Datenbindung
        dgvChild.DataSource = dtchild
        dgvParent.DataSource = dtparent
 
    End Sub
 
 
 
    Private Sub dtchild_RowChanged(sender As Object, _
            e As System.Data.DataRowChangeEventArgs) _
            Handles dtchild.RowChanged
 
       'Parentrow anhand der Relation für aktuell geänderte Zeile
       Dim parentrow As DataRow = e.Row.GetParentRow("SatzID")
       If parentrow Is Nothing Then Exit Sub
 
       'Alle Childrows zu der Parentrow ermitteln
       Dim rows() As DataRow = parentrow.GetChildRows("SatzID")
 
       'Childrows aggregieren: Summe
       parentrow("Summe") = Aggregate r As DataRow In rows _
                            Into Sum(CDbl(r("Menge").ToString))
 
 
 
       'Alternative (beim Wechsel des SatzID im Childsatz)
        With dtparent
            For i As Integer = 0 To .Rows.Count - 1
               Dim ch_rows() As DataRow = .Rows(i).GetChildRows("SatzID")
               .Rows(i)("Summe") = Aggregate r As DataRow In ch_rows _
                                   Into Sum(CDbl(r("Menge").ToString))
            Next i
        End With
 
End Class