Private Sub btnEintragen_Click(ByVal sender As Object, ByVal e As _
  System.Windows.RoutedEventArgs) Handles btnEintragen.Click
grid.SelectAllCells()
grid.ClipboardCopyMode = DataGridClipboardCopyMode.IncludeHeader
ApplicationCommands.Copy.Execute(vbNull, grid)
grid.UnselectAllCells()
Dim result As String
result = Clipboard.GetData(DataFormats.CommaSeparatedValue)
Clipboard.Clear()
Dim file As New StreamWriter("c:\test.csv")
file.WriteLine(result)
file.Close()
end sub