MasterDetailPage - can't find any way to target 'detail' page window - xamarin

Question

I have created a Master Detail Page
I am loading a list of items into the 'detail' frame / window
I want to replace the contents of that page with a template / view which never has any reason to exist as an item in the Menu Items
I have tried replacing MainPage and Navigation which load the page but you lose the Master Detail context - the menu
Please can someone tell me what I call in order to replace the current page with one of my choice while staying within the context of Master Detail?
This does not work, for example - it removes the MasterDetail menu
Navigation.PushAsync(new Arcade.Index());
I have created the MasterDetailPage by pretty much letting Visual Studio generate it. I set it after a successful login, like so:
var welcome = new Pages.Welcome();
Application.Current.MainPage = welcome;
This is an excerpt of the XAML for Welcome
<MasterDetailPage.Master>
<pages:WelcomeMaster x:Name="MasterPage" />
</MasterDetailPage.Master>
<MasterDetailPage.Detail>
<NavigationPage>
<x:Arguments>
<pages:Index />
</x:Arguments>
</NavigationPage>
I've added this to the code behind for Welcome
InitializeComponent();
MasterPage.ListView.ItemSelected += ListView_ItemSelected;
this.Detail = new NavigationPage(new Arcade.Index());
In spite of all that, when I call this later, the MasterDetail menu disappears
((MasterDetailPage)Application.Current.MainPage).Detail = new Arcade.Index();

Answer 1

In you App.xaml.cs add static method then you can use it to navigate in you code
public static void SetDatailPage(Page page)
{
if (App.Current.MainPage is MasterDetailPage)
{
var masterPage = (MasterDetailPage)App.Current.MainPage;
masterPage.Detail = new NavigationPage(page);
}
}
And use it like this
App.SetDatailPage(new YourPageYouWannaNavigateTo());

Answer 2

1 - use App.Current.Mainpage
var md = (MasterDetailPage)App.Current.MainPage;
md.Detail = new MyPage();
2 - use navigation
when you initially create your detail, wrap it in a NavigationPage
this.Detail = new NavigaitionPage(new Page1());
then later, Page1 can navigate to Page2 within the Detail pane
Navigation.PushAsync(new Page2());
3 - explicitly pass a reference to the MasterDetailPage
// when you create Page1, pass a reference to the MasterDetailPage
// you will also need to modify Page1's constructor
this.Detail = new Page1(this);