Clipboard does not copy/paste objects when complied with .Net8

[cornerbowlsoftware]

Describe the bug

Clipboard does not copy/paste objects when complied with .Net8

To Reproduce

Create a new Avalonia project.
Set the targets to:
<TargetFramework>net7.0</TargetFramework>
Create a model that includes the [Serializable] attribute. For example:

    [Serializable]
    public class MyTestModel
    {
        public int Id { get; set; }
        public string? Name { get; set; }

        public MyTestModel() 
        { 
        }
    }

Update the MainView to create the model and copy then paste the model to and from the clipboard like so:

public partial class MainView : UserControl
{
    public MainView()
    {
        InitializeComponent();
        Loaded += MainView_Loaded;
    }

    private void MainView_Loaded(object? sender, Avalonia.Interactivity.RoutedEventArgs e)
    {
        TestAsync().GetAwaiter().GetResult();
    }

    private async Task TestAsync()
    {
        var m = new MyTestModel()
        {
            Id = 1,
            Name = "Test",
        };

        var dataObject = new DataObject();
        dataObject.Set("my-app-person", m);

        var clipboard = TopLevel.GetTopLevel(this)!.Clipboard!;
        await clipboard.SetDataObjectAsync(dataObject);

        var r = await clipboard.GetDataAsync("my-app-person");
        Debug.WriteLine(r);
    }
}

Run the program. Notice the variable "r" is returned as expected.
Modify both Avalonia projects to target:
<TargetFramework>net8.0</TargetFramework>
Run the program. Notice the variable "r" is null.

Expected behavior

The value should be returned.

Avalonia version

11.0.11

OS

Windows

Additional context

No response

[timunie]

Please don't do GetAwaiter.getresult. I told you before. Instead make OnLoaded async void (this is allowed) and call the function via await

[kekekeks]

IIRC BinaryFormatter got deprecated or disabled with net8.0. Do not rely on the old .NET binary serialization when using modern .NET runtimes

[maxkatz6]

Yes, it's not going to be supported anymore.
We might provide some plug-in data-object serializer/deserializer. But generally, you should do it on your app side passing byte array to the API.

[cornerbowlsoftware]

@kekekeks and @maxkatz6 my WPF apps work as expected. This bug appears to be specific to Avalonia.

Thanks.

[timunie]

Please upload a minimum sample using latest nightly builds. Don't use GetAwaiter in the test project. Thanks.

[cornerbowlsoftware]

@timunie please see the following sample application that exposes the bug.

AvaloniaClipboardBug.zip

[maxkatz6]

@cornerbowlsoftware

This bug appears to be specific to Avalonia.

FYI, dotnet/announcements#293
Also https://learn.microsoft.com/en-us/dotnet/core/compatibility/serialization/8.0/binaryformatter-disabled

[cornerbowlsoftware]

@maxkatz6 Yes, I already saw that, however, my .Net8 WPF app works. The bug is specific to Avalonia. There is something else going on.

[IanRawley]

Previous behavior

In .NET 7, the BinaryFormatter.Serialize(Stream, Object) and BinaryFormatter.Deserialize(Stream) methods were marked obsolete and raised an error at compile time. However, if your application suppressed the obsoletion, it could still call the methods and they functioned properly in most project types (excluding >ASP.NET, WASM, and MAUI). For example, the APIs functioned correctly in a console app.

New behavior

Starting in .NET 8, the affected methods throw a NotSupportedException at run time across all project types except Windows Forms and WPF. The APIs continue to remain >obsolete (as error) across all project types, including Windows Forms and WPF.

From the second link. This is not a bug with Avalonia, it's WPF behaving differently to everything else.

[cornerbowlsoftware]

@IanRawley ok so you are saying even though .Net 8 Windows and 4.7.2 WPF are able to do it, the underlying platform specific libraries in Avalonia are unable to utilize the functionality .Net 8 Windows is using? Ok. I don't need inter-application copy paste so it was super easy to simply use a singleton to save my objects for later pasting.

[timunie]

@cornerbowlsoftware yep. That's what the NET team did. Disabled it for anyone except WPF and WinForms. We cannot change that from our side. But there's a switch for you to enable it again.

[kekekeks]

Again, it's not a bug, it's a critical security vulnerability that got fixed by Microsoft.
You can re-enable the formatter by adding <EnableUnsafeBinaryFormatterSerialization>true</EnableUnsafeBinaryFormatterSerialization> to your project file if you wish to voluntarily subject your users to a risk, but we won't be setting this flag from Avalonia package

[kekekeks]

Not a bug, people who don't care about security can re-enable the feature as documented here.

Note that the API will be removed from .NET 9 entirely, so fix your apps.

[cornerbowlsoftware]

@timunie and @kekekeks Ok thanks for letting me know. I already moved away and just save the copied object to a singleton. I'll do the same in my WPF app. Thanks for the heads up.