TabbedPage UI is not refreshed

Hello,
I have a little problem with a TabbedPage UI refresh.

`
public void RefreshList()
{
Children.Clear();
this.IsBusy = true;
this.Title = "Loading data ........";

    LoadData();   // <----------- here is the Datarefresh from a webservice
        Children.Add(new ListPage(NodeList) { Title = "List", Icon = "List.png" });
        Children.Add(new MapPage(NodeList) { Title = "Map", Icon = "Map.png" });
        Children.Add(new InfoPage() { Title = "Info", Icon = "Info.png" });
        this.IsBusy = false;

`
Everything works fine. BUT, the "Children.Clear()" and " this.Title = "Loading data ........";" is not showed, the UI is not refreshed.
The UI is "frozen" until the RefreshList() ends. After that, the new Data is shown. Under Windows I would call a Application.DoEvents()
before LoadData() is called, but I have no idea how to do that under XForms.

Best regards Axel