Private VersionNr As String
    Property pVersionNr() As String
        Get
            Return VersionNr
        End Get
        Set(ByVal Value As String)
            Dim Wertok As Boolean = True
            For Each c As Char In Value
                If Not ((Char.IsDigit(c)) Or c = ".") Then
                    Wertok = False
                End If
            Next c
 
            If Wertok = True Then
                VersionNr = Value
            Else
                tbxVersionsNr.Text = VersionNr
            End If
        End Set
    End Property

    Private Sub tbxVersionsNr_TextChanged(ByVal sender As System.Object, ByVal _
      e As System.EventArgs) Handles tbxVersionsNr.TextChanged
 
        pVersionNr = tbxVersionsNr.Text
    End Sub