Login and MasterDetail Interaction

HI.

In the App class contructor i got

MainPage = new LogInPage(); ,

them, in the login page when the user press the button login i use:

BUTTON_LOGIN.Clicked += async(sender, ea) => {
        App.Current.MainPage = new RootPage();   
}

and in the RootPage contructor:

Master = new MenuPage();
Detail = new NavigationPage (new HomePage ())

when the the logout button its called in the menuPage y use:
App.Current.MainPage = new LogInPage ();

but nothing happens. Any ideas?