Proposal: WinUI 3 - File New Project Template should create a `MainPage` and not just a MainWindow

_Originally posted by @michael-hawker in https://github.com/microsoft/microsoft-ui-xaml/issues/4966#issuecomment-882958799_

Yeah, I too keep getting tripped up that Window isn’t a DependencyObject… it’s a bit weird.

If the expectation that Window is supposed to just be the host like the implicit Frame created in App.xaml.cs for UWP apps, maybe the File -> New template for WinUI 3 should separate out the MainWindow as also having a MainPage class hosted by it already setup?

This would help lead developers to the proper constructs when building their app and set them up for success vs. having everyone start dumping UI in MainWindow and then getting frustrated.

I mean I really like how the MainWindow is more exposed compared to all the extra logic on Startup that was done in the UWP space, but it’s super confusing and bare-bones template when trying to start building an app from afterwards without creating a new Page first.

I keep seeing a few issues filed because of this (and have been tripped up myself) by the fact that the default project template for WinUI 3 creates a bare Window class.

This doesn’t jive as well with many UI APIs as it’s not a DependencyObject/FrameworkElement. It’s really just the application ‘shell’, like the implicit Frame that UWP apps used to create back in App.xaml.cs.

I love that this Window is now exposed and more easily customizable via XAML, but feel like it should still host a Frame which then points to a MainPage object based on Page where a developer is then led to start creating their application’s UI.

Otherwise, developers just start building UI within the Window itself and get tripped up when something needs to navigate the visual tree or try to create a DependencyProperty off of it (see #4966 for instance).

[michael-hawker]

If anything, the template could just create a MainPage and reference it in the Window XAML:

<Window x:Class="ProjectTemplate.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:local="using:ProjectTemplate"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d">

    <!--  Window isn't a FrameworkElement for dependency property or resources...  -->
    <local:MainPage />
</Window>

This is what I did in my template (though I’m also sharing the MainPage with the UWP head in the case anyway): https://github.com/michael-hawker/WinUI2Plus3Template/blob/main/ProjectTemplate.WinAppSDK/MainWindow.xaml

Though in the onboarding/getting started docs there should still be information here about how to setup and use a Frame model (if needed) like what is setup by default in a UWP app or alternatively hosting a NavigationView with a Frame inside it. Though it definitely needs to be called out somewhere that Window isn’t mean to be used with XAML markup constructs, see folks running into this pitfall, mostly with binding, all the time.

[crramirez]

Ok, I will begin with that. I agree with you that this could help everyone to migrate a UWP app to WinUI 3 easier.

I copied the stats from another user 😏 . This is the code:

![Carlos Ramirez's GitHub Stats](https://github-readme-stats.vercel.app/api?username=crramirez&show_icons=true&count_private=true)