Hi, I looked in app.xaml.cs file in net 9 and create instance of main window change to: protected`` override Window CreateWindow(IActivationState? activationState) { return`` new Window(new AppShell()); } is must? why this change? Is releavant for mac and windows ? Thanks,

Why the Change? In .NET 9, you use CreateWindow to set up the main window. This helps manage the app lifecycle better and supports multiple windows. Is It Necessary? Yes, it’s required in .NET 9. The old MainPage property is deprecated. Relevance for Mac and Windows This change applies to both macOS and Windows. Here’s the code: protected override Window CreateWindow(IActivationState? activationState) { return new Window(new AppShell()); }

new main window in net 9 changed

Accepted answer

Ki-lianK-7341 770 Reputation points

2025-01-27T07:56:45.5166667+00:00
Why the Change?

In .NET 9, you use CreateWindow to set up the main window. This helps manage the app lifecycle better and supports multiple windows.

Is It Necessary?

Yes, it’s required in .NET 9. The old MainPage property is deprecated.

Relevance for Mac and Windows

This change applies to both macOS and Windows.

Here’s the code:

protected override Window CreateWindow(IActivationState? activationState) { return new Window(new AppShell()); }
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1 person found this answer helpful.
Dani_S 4,016 Reputation points

2025-01-27T07:59:18.8733333+00:00

How i can make multiple windows?

Ki-lianK-7341 770 Reputation points

2025-01-27T08:05:16.17+00:00

To create multiple windows in .NET 9, you can follow these steps:

Override CreateWindow Method:

In your App.xaml.cs, override the CreateWindow method to create the main window.

Create Additional Windows:

Define additional windows in your project.

Open New Windows:

Use the Window class to create and show new windows.

Dani_S 4,016 Reputation points

2025-01-27T08:12:55.48+00:00

Is there any documentation for this issue ?

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 47,766 Reputation points Microsoft Vendor

2025-01-28T01:29:02.8433333+00:00

Thanks for your feedback.

Maui officials provided an explanation on why MainPage was changed to Windows in MainPage.

MainPage Instead of defining the first page of your app using the MainPage property on an Application object, you should set the Page property on a Window to the first page of your app. This is what happens internally in .NET MAUI when you set the MainPage property, so there's no behavior change introduced by the MainPage property being marked as obsolete. The following example shows setting the Page property on a Window, via the CreateWindow override:

public partial class App : Application { public App() { InitializeComponent(); } protected override Window CreateWindow(IActivationState? activationState) { return new Window(new AppShell()); } }

Code that accesses the Application.Current.MainPage property should now access the Application.Current.Windows[0].Page property for apps with a single window. For apps with multiple windows, use the Application.Current.Windows collection to identify the correct window and then access the Page property. In addition, each element features a Window property, that's accessible when the element is part of the current window, from which the Page property can be accessed (Window.Page). Platform code can retrieve the app's IWindow object with the Microsoft.Maui.Platform.GetWindow extension method. While the MainPage property is retained in .NET MAUI 9 it will be completely removed in a future release.

Dani_S 4,016 Reputation points

2025-01-28T17:15:49.96+00:00

Hi,

In my Mac I have this code:

is it correct in net 9?

protected override Window CreateWindow(IActivationState activationState)

{

Window window = base.CreateWindow(activationState);

try

{

window.Stopped += async(s,e) =>

{

if (!string.IsNullOrEmpty(LoginConfigurations.GetInstance().SessionToken ))

{

var container = new Bootstrapper().Bootstrap();

IAutomationApiClient automationApiClient = container.Resolve<IAutomationApiClient>();

var results = await automationApiClient.PostLogOut($"{LoginConfigurations.GetInstance().Portal}/api/GSPortal/PostLogOut/false", LoginConfigurations.GetInstance().SessionToken);

if(results)

{

App.Current.Quit();

}

}

};

}

catch (Exception)

{

}

return window;

}

}
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