> For the complete documentation index, see [llms.txt](https://functionzero.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://functionzero.gitbook.io/docs/libraries/maui.mvvmzero/walkthrough/launching-our-app.md).

# Launching our app!

To get our application off the ground, we need to set the top-level UI element. Our options are as follows:

* A single fixed `ContentPage`
* A root `NavigationPage` that can *Push* and *Pop* other pages
* A `TabbedPage`
* A `FlyoutPage` (advanced)
* Anything that derives from `Microsoft.Maui.Controls.Page`

For this sample we're going to use a `TabbedPage`, or more specifically, an `AdaptedTabbedPage`, because at the time of writing, the `TabbedPage` is unsuitable on the `Windows` platform until [this bug](https://github.com/dotnet/maui/issues/14572) is fixed

Open `App.xaml.cs` and replace the content with the following:

```csharp
using FunctionZero.Maui.MvvmZero;
using MvvmZeroTutorial.Mvvm.PageViewModels;

namespace MvvmZeroTutorial
{
    public partial class App : Application
    {
        public App(IPageServiceZero pageService)
        {
            InitializeComponent();
            
            // Don't forget to call pageService.Init, or navigation will not work properly!
            pageService.Init(this);
            
            var rootPage = pageService.GetMultiPage(VmInitializer, typeof(ReadyPageVm), typeof(SteadyPageVm), typeof(GoPageVm));
            var a = new ContentPage();
            MainPage = rootPage;
        }

        private bool VmInitializer(object viewModel)
        {
            if (viewModel is ReadyPageVm)
                return false; // Do not wrap the ReadyPage in a NavigationPage.

            return true;
        }
    }
}

```

There are a few things going on here. We're injecting an `IPageServiceZero` into the constructor, but we didn't register it, what gives? The `UseMvvmZero` in `MauiProgram.cs` call registers the `IPageServiceZero` implementation for us. Note: `NavigationPage` is also registered, because it is used internally. Everything else is our responsibility, including the `MultiPage`!

`MvvmZero` delegates the creation and lifetime of objects to the container, so when we call `GetMultiPage` we get back whatever we registered for `MultiPage<Page>`, in this case a *Singleton* `AdaptedTabbedPage`

The first parameter is a `Func` that is called for each `PageVm` we want to present. It should return `true` if we want the corresponding `ContentPage` wrapped in a `NavigationPage` (so we can push pages on to it) or `false` otherwise.&#x20;

In this sample, the first `Tab` does not support a navigation stack, the others do.

Build and run, and you ought to see an app with a root `TabbedPage` containing 3 tabs.