Calling C# Method from javascript error => "App is not defined"

In the following sample code i have defined the Method “SwitchNB” which should show or hide the NavigationBar:

public partial class Startseite : Page
    {
        public Startseite()
        {
            InitializeComponent();
        }

        //—————————–
        // Publish WebMethods
        //————————–—
        protected override void OnWebRender(dynamic config)
        {
            base.OnWebRender((object)config);
            config.webMethods = new[] { “SwitchNB” };
            RegisterWebMethods(config);
        }

        //——————————–
        // NavigationBar ON/OFF
        //——————————–
        [WebMethod]
        public void SwitchNB()
        {
            navigationBar1.Visible = !navigationBar1.Visible;
        }

In my HTML-Code i have defined a Button which is calling the Javascript “callwise()”:

<script type=”text/javascript”>
    function callwise()
{
        App.Startseite.SwitchNB();
    }
</script>

When I’m pressing the button I will get the following Error Mesaage in the Browser console window: (Browser1.png)

  Uncaught ReferenceError: App is not defined

When I’m inserting tha call manually  in the console window the call is working: (Browser2.png)

What am I doing wrong ????