Programmatically way to Bootstrap Windows Platform in pure C#

[jvelilla]

Description

Is there any reliable way to programmatically bootstrap the .NET MAUI windows platform in pure C# without using XAML?

By default, the bootstrap code for the Windows platform uses App.xaml and the code behind App.xaml.cs.

The goal is to learn the bootstrap to initialize the Application in pure C# because I want to use a different programming language and avoid XAML dependencies, initially for proof of concept.

Steps to Reproduce

Git branch with the existing code

To reproduce

1. Create a default project.
2. Delete from /Platforms)/Windows/ the files App.xaml and App.xaml.cs.
3. Create a new class App.cs

with the following code.

using Microsoft.Maui;
using Microsoft.UI.Xaml;

// To learn more about WinUI, the WinUI project structure,
// and more about our project templates, see: http://aka.ms/winui-project-info.

namespace ExampleMauiApp.WinUI;

/// <summary>
/// Provides application-specific behavior to supplement the default Application class.
/// </summary>
public class App : MauiWinUIApplication
{
	/// <summary>
	/// Initializes the singleton application object.  This is the first line of authored code
	/// executed, and as such is the logical equivalent of main() or WinMain().
	/// </summary>
	public App()
	{
        }
    protected override MauiApp CreateMauiApp() => MauiProgram.CreateMauiApp();
}

Expected: Windows bootstrap initialization
Actual output: compile error.

Version with bug

6.0.400 (current)

Last version that worked well

Unknown/Other

Affected platforms

Windows

Affected platform versions

Windows

Did you find any workaround?

No response

Relevant log output

Build started...
...
1>CSC : error CS5001: Program does not contain a static 'Main' method suitable for an entry point
1>Done building project "ExampleMauiApp.csproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Depends on

• https://github.com/microsoft/WindowsAppSDK/discussions/2691

VS bug #1863736

[ericsink]

As far I can tell, the short answer to your question is: No.

I've been investigating a Swift projection for WinRT-ish things, including Windows App SDK. I came with the expectations I obtained from past work with the Xamarin Forms flavor of XAML, where everything can be done in pure code without XAML syntax. But for WinUI3 XAML, things are very different.

There is some "magic" associated with the Application class, and it seems to be related to the IXamlMetadataProvider interface. I'm still figuring out how things work.

See also:

microsoft/WindowsAppSDK#2691

and:

microsoft/windows-app-rs#50

[hartez]

The code generated from the XAML includes the missing "Main" method, but you can add your own to the class manually:

static void Main(string[] args)
{
    Microsoft.UI.Xaml.Application.Start((p) => new App());
}

(I've done this before with UWP apps.)

But you'll still run into issues with missing XAML resources for all the controls; some from WinUI, and some supplemental ones from MAUI. I don't know of a way to get those included; trying to create the resource dictionaries manually just throws a COMException.

[mattleibow]

@PureWeen I think you did this with the Fabulous peoples? Basically disable the something and then copy-paste the code from before?

[homeyf]

Verified this issue with Visual Studio Enterprise 17.7.0 Preview 5.0. Can repro on windows platform with sample Project.
branch

[mattleibow]

Closing this issue as it is unrelated to .NET MAUI and more related to WinUI and how things are set up.

Please open an issue here: v