Dim first As Boolean = True
        Dim dt As DataTable = dt1.Copy()
 
        Dim dv As New DataView(dt)
        dv.RowFilter = "CustomerID='LILAS'"
        Dim sumFreight As Double
        Dim tal As New ArrayList
        For Each drv As DataRowView In dv
            sumFreight += CDbl(drv("Freight"))
            If Not first Then tal.Add(drv.row)
            first = False
        Next
 
        For Each dr As DataRow In tal
            dr.Delete()
        Next
 
        If sumFreight > 0 Then
            ' "Ersatz"-Zeile schreiben
            dv(0)("ShipName") = "Sum of freight"
            dv(0)("Freight") = sumFreight.ToString()
        End If
        DataGrid1.DataSource = dt

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Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist