Failed to open designer

Environment

Version 17.3.0 Preview 1.0

.NET version

net7.0

Did this work in a previous version of Visual Studio and/or previous .NET release?

No response

Issue description

Seeing

[18:37:53.343110] fail: System.InvalidOperationException: Can't resolve types until ITypeIdentityResolutionService has started processing enqueued assemblies.
                           at Microsoft.DotNet.DesignTools.Protocol.Types.AssemblySearchingTypeIdentityResolutionService.TryGetType(TypeIdentity typeIdentity, Boolean ignoreCase, Type& type)
                           at Microsoft.DotNet.DesignTools.Protocol.Types.AssemblySearchingTypeIdentityResolutionService.ResolveNamedType(TypeIdentity typeIdentity, TypeIdentityResolutionOptions options)
                           at Microsoft.DotNet.DesignTools.Protocol.Types.TypeIdentityResolutionService.ResolveType(TypeIdentity typeIdentity, TypeIdentityResolutionOptions options)
                           at Microsoft.DotNet.DesignTools.Client.Types.BaseTypeResolutionService.GetType(String name, Boolean throwOnError, Boolean ignoreCase)

                        For information on how to troubleshoot the designer refer to the guide at https://aka.ms/winforms/designer/troubleshooting.
[18:37:53.450100] fail: REQUEST FAILURES: Sessions/EndLoad
                        Microsoft.DotNet.DesignTools.Client.DesignToolsServerException: 'Site' must not be null in order to access a required service.

                        For information on how to troubleshoot the designer refer to the guide at https://aka.ms/winforms/designer/troubleshooting.

Steps to reproduce

Take sample app from https://github.com/dotnet/winforms/issues/6952 and open in the designer.

Diagnostics

No response

[RussKie]

1. add

<ItemGroup>
    <Reference Include="c:\winforms\artifacts\bin\System.Windows.Forms\Debug\net7.0\System.Windows.Forms.dll" />
    <Reference Include="c:\winforms\artifacts\bin\System.Windows.Forms.Primitives\Debug\net7.0\System.Windows.Forms.Primitives.dll" />
  </ItemGroup>

This isn’t a supported use case, so we can’t really offer much help. I can sort of see how the SDK and VS can get confused here. If you wish to test the latest Windows Forms runtime with the designer you’d need to copy the changes to the SDK. I’ve written a script for this https://gist.github.com/RussKie/bb11e213f04729603e533856865922c1.

Feel free to reopen if you see the issue in an app without referencing the canary bits.

[kant2002]

I would guess that issue here https://github.com/dotnet/winforms/blob/9ea06044776cd10bd1968ee141449bed1a8e6945/src/System.Windows.Forms/src/System/Windows/Forms/CursorConverter.cs#L88

This condition is false when Cursor comes from assembly with different identity(unsure). Because .NET can treat this is as different Cursor classes, it falls down to https://github.com/dotnet/winforms/blob/9ea06044776cd10bd1968ee141449bed1a8e6945/src/System.Windows.Forms/src/System/Windows/Forms/CursorConverter.cs#L146

which just calls object.ToString().