Protected Function Saveable() As Boolean
        Dim msg As New ArrayList
 
        GetSaveCriteria(msg)
 
        If Not msg.Count = 0 Then
            Dim text As String = ""
            For Each s As String In msg
                text &= s & System.Environment.NewLine
            Next
 
            MessageBox.Show("Es kann nicht gespeichert werden!" & _
              System.Environment.NewLine & _
            "es wurde: " & System.Environment.NewLine & _
            text, _
            "Speichern nicht möglich", MessageBoxButtons.OK, _
            MessageBoxIcon.Information, MessageBoxDefaultButton.Button1)
            Return False
 
        End If
 
        Return True
    End Function
 
    Protected Overridable Sub GetSaveCriteria(ByRef msg As ArrayList)
 
    End Sub

    Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles btnSave.Click
        If Not saveable Then Return
...

    Protected Overrides Sub GetSaveCriteria(ByRef msg As ArrayList)
        If txt_Name.Text = "" Then
            msg.Add("kein Name angegeben")
        End If
    End Sub