wpf throw Could not load file or assembly 'System.Windows.Forms exception on starting if published with --self-contained

[alraseensaad]

Description

When I run the wpf application it throw
Could not load file or assembly 'System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. The system cannot find the file specified.
if any third party need System.Windows.Forms when I publish the application using --self-contained and works fine if --self-contained=false

Reproduction Steps

Create a new wpf project and references it for example Microsoft.AppCenter which requires System.Windows.Forms

configure the AppCenter on startup

 public partial class App : Application
 {
     public App()
     {
         Application.Current.DispatcherUnhandledException += Current_DispatcherUnhandledException;
     }

     private void Current_DispatcherUnhandledException(object sender, System.Windows.Threading.DispatcherUnhandledExceptionEventArgs e)
     {
         MessageBox.Show(e.Exception.Message);
     }

     protected override void OnStartup(StartupEventArgs e)
     {
         base.OnStartup(e);
         SetAppCenter();
     }
     private void SetAppCenter()
     {
         Microsoft.AppCenter.AppCenter.Start("null",
                    typeof(Microsoft.AppCenter.Analytics.Analytics), typeof(Crashes));

     }

 }

Expected behavior

To run normally like self-contained=false publishing

Actual behavior

It throws exception
Could not load file or assembly 'System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'. The system cannot find the file specified.

Regression?

It works if I publish the using self-contained=false

Known Workarounds

No response

Impact

No response

Configuration

dotnet 9
windows 11
x64

Other information

WpfApp9-master.zip

[lindexi]

@alraseensaad It is the Microsoft.AppCenter 's issues, not wpf issues. Because the Microsoft.AppCenter reference the System.Windows.Forms, Version=4.0.0.0 assembly which cause this exception.

The main break code is in ApplicationLifecycleHelperDesktop cctor:

	static ApplicationLifecycleHelperDesktop()
	{
		... 
		System.Windows.Forms.Application.ApplicationExit += delegate
		{
			WindowsHelper.OnMinimized -= _OnMinimizedDelegate;
		};
	}

And you do not add the UseWindowsForms to csproj, which will ignore the System.Windows.Forms.dll file when publish with self contained.

How to fix?

Adding the <UseWindowsForms>true</UseWindowsForms> to csproj or fix the Microsoft.AppCenter NuGet package.

[himgoyalmicro]

@alraseensaad Does @lindexi suggestion solves your issue ?

[alraseensaad]

@lindexi

I just give the Microsoft.AppCenter as examples to reproduce the problem but it does not work for any third-party that depend on Windows Form and the problem is that as it self contained it show includes all needed references as it was before dotnet 9

Also it works in dotnet 8 without using <UseWindowsForms>true</elf contained>

and My project is Wpf why to UseWindowsForms which will show all WindowsForms staff on the development environment

[lindexi]

@alraseensaad The main reason is the builder will not output WinFroms.dll when its UseWindowsForms reference is not set in dotnet 9