Protected Overrides Function IsModified() As Boolean 
        Dim ret As Boolean = MyBase.IsModified()
        ' Enter your custom processing code here. 
        Return ret

    End Function 'IsModified
End Class 'UrlConfigElement 

protected override bool IsModified()
{
    bool ret = base.IsModified();
    // You can enter your custom processing code here. 
    return ret;
}

    ' Show how to use IsModified. 
    ' This method modifies the port property 
    ' of the url element named Microsoft and 
    ' saves the modification to the configuration 
    ' file. This in turn will cause the overriden 
    ' UrlConfigElement.IsModified() mathod to be called.  
    Shared Sub ModifyElement()
        Try 
            ' Get the current configuration file. 
            Dim config _
            As System.Configuration.Configuration = _
            ConfigurationManager.OpenExeConfiguration( _
            ConfigurationUserLevel.None)

            ' Get the MyUrls section. 
            Dim myUrlsSection As UrlsSection = _
            config.GetSection("MyUrls")


            Dim elements As UrlsCollection = _
            myUrlsSection.Urls


            Dim elemEnum As IEnumerator = _
            elements.GetEnumerator()

            Dim i As Integer = 0
            While elemEnum.MoveNext()
                If elements(i).Name = "Microsoft" Then
                    elements(i).Port = 1010
                    Dim [readOnly] As Boolean = _
                    elements(i).IsReadOnly()
                    Exit While 
                End If
                i += 1
            End While 

            If Not myUrlsSection.ElementInformation.IsLocked Then

                config.Save(ConfigurationSaveMode.Full)

                ' This to obsolete the MyUrls cached  
                ' section and read the updated version  
                ' from the configuration file.
                ConfigurationManager.RefreshSection("MyUrls")
            Else
                Console.WriteLine("Section was locked, could not update.")
            End If 

        Catch err As ConfigurationErrorsException
            Console.WriteLine("[ModifyElement: {0}]", _
            err.ToString())
        End Try 

    End Sub 'ModifyElement

// Show how to use IsModified. 
        // This method modifies the port property 
        // of the url element named Microsoft and 
        // saves the modification to the configuration 
        // file. This in turn will cause the overriden 
        // UrlConfigElement.IsModified() mathod to be called.  
        static void ModifyElement()
        {
            try
            {
                // Get the configuration file.
                System.Configuration.Configuration config =
                    ConfigurationManager.OpenExeConfiguration(
                    ConfigurationUserLevel.None);

                // Get the MyUrls section.
                UrlsSection myUrlsSection =
                    config.GetSection("MyUrls") as UrlsSection;


                UrlsCollection elements = myUrlsSection.Urls;


                IEnumerator elemEnum =
                    elements.GetEnumerator();

                int i = 0;
                while (elemEnum.MoveNext())
                {
                    if (elements[i].Name == "Microsoft")
                    {
                        elements[i].Port = 1010;
                        bool readOnly = elements[i].IsReadOnly();
                        break;
                    }
                    i += 1;
                }

                if (!myUrlsSection.ElementInformation.IsLocked)
                {

                    config.Save(ConfigurationSaveMode.Full);

                    // This to obsolete the MyUrls cached  
                    // section and read the updated version 
                    // from the configuration file.
                    ConfigurationManager.RefreshSection("MyUrls");
                }
                else
                    Console.WriteLine(
                        "Section was locked, could not update.");
            }

            catch (ConfigurationErrorsException err)
            {
                Console.WriteLine("[ModifyElement: {0}]",
                    err.ToString());
            }

        }