Windows Forms Out-of-process designer can't make use of transitive references

Environment

Visual Studio Professional 2022 (64-bit) Version 17.4.0

.NET version

.NET 6.0

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

Works as soon as .NET Framework is used in the same projects. Does also work with multitargeting.

Issue description

The new out-of-process Windows Forms designer shows the following error when the base form of the form that is currently opened in the designer implements an interface from a transitive referenced project:

It took me quite a while to hunt this down but it seems that the new designer shows this error if …

• the form in question is derived from a base form (from the same or another project)
• the base form implements an interface
• the interface is defined in another project
• the other project is referenced over an transient project reference

In this case the base form still can be designed. The designer however crashes when openening the derived form. The error disappears as soon a direct project reference is added.

References overview

---

More details and a repro under https://github.com/awaescher/DesignerVsInterfaces

Steps to reproduce

• clone the repository https://github.com/awaescher/DesignerVsInterfaces
• build
• open the designer for both base forms: should work
• open the designer for GoodDerivedForm: should work
• open the designer for BadDerivedForm: should cause the error shown above

Diagnostics

// complete log when opening BadDerivedForm from the repro repository

[09:19:17.934946] info: Creating VsDesignerLoader
[09:19:17.938946] trce: Sending request: Sessions/Create
[09:19:17.939981] trce: Sessions/Create took 00:00:00.0015269.
[09:19:17.940945] trce: Sending request: Options/SetOptions
[09:19:17.940945] trce: Options/SetOptions took 00:00:00.0007348.
[09:19:17.941961] trce: Sending request: Sessions/BeginLoad
[09:19:17.941961] trce: Sessions/BeginLoad took 00:00:00.0005457.
[09:19:17.959431] trce: Sending request: Sessions/DesignerActivated
[09:19:17.960400] trce: Sessions/DesignerActivated took 00:00:00.0007037.
[09:19:18.044542] info: Created VsCodeDomProvider for 'C:\Users\daw\Source\repos\DesignerVsInterfaces\DesignerVsInterfacesUI\BadDerivedForm.cs'
[09:19:18.049542] info: Created VsCodeDomProvider for 'C:\Users\daw\Source\repos\DesignerVsInterfaces\DesignerVsInterfacesUI\BadDerivedForm.Designer.cs'
[09:19:18.050543] trce: ProcessNamespace: DesignerVsInterfacesUI
[09:19:18.051543] trce: ProcessClass: BadDerivedForm
[09:19:18.052543] trce: ProcessConstructor
[09:19:18.053542] trce: ProcessNamespace: DesignerVsInterfacesUI
[09:19:18.054542] trce: ProcessClass: BadDerivedForm
[09:19:18.055542] trce: ProcessField: components
[09:19:18.057542] trce: ProcessMethod: Dispose
[09:19:18.058543] trce: ProcessMethod: InitializeComponent
[09:19:18.059542] trce: Sending request: Sessions/FindDesignableClass
[09:19:18.061560] trce: Sessions/FindDesignableClass took 00:00:00.0022300.
[09:19:18.061560] fail: Request failures: Sessions/FindDesignableClass.
                        Microsoft.DotNet.DesignTools.Client.DesignToolsServerException: The designer could not be shown for this file because none of the classes within it can be designed.  The designer inspected the following classes in the file: \r\n
                        	BadDerivedForm --- The base class 'DesignerVsInterfacesUI.BaseFormReferencingBaseLibrary' could not be loaded.  Ensure the assembly has been referenced and that all projects have been built.

                        For information on how to troubleshoot the designer refer to the guide at https://aka.ms/winforms/designer/troubleshooting.
[09:19:18.065425] trce: Updating selection in server process.
[09:19:18.065425] trce: Sending request: Selection/UpdateSelection
[09:19:18.066433] trce: [DesignerVsInterfacesUI]: Attempting to update selection: 0 components, Replace
[09:19:18.066433] trce: [DesignerVsInterfacesUI]: Made change: False
[09:19:18.066433] trce: Selection/UpdateSelection took 00:00:00.0007927.
[09:19:18.066433] trce: Sending request: Sessions/Unload
[09:19:18.067067] trce: Sessions/Unload took 00:00:00.0004503.
[09:19:18.067067] trce: Sending request: Sessions/EndLoad
[09:19:18.067067] trce: Sessions/EndLoad took 00:00:00.0004010.
[09:19:23.422459] trce: [DesignerVsInterfacesUI]: Sending request to remove roots:
                          - 289: 1 root(s).
                          ...
                          - 1d9: 2 root(s).
                          - 1d8: 6 root(s).
                        
[09:19:23.422459] trce: Sending request: Objects/RemoveObjectRoots
[09:19:23.425472] trce: [DesignerVsInterfacesUI]: Objects/RemoveObjectRoots request received for 293 object(s).
                          - 289: 1 root(s).
                          ...
                          - 1d9: 2 root(s).
                          - 1d8: 6 root(s).
                        
[09:19:23.425472] trce: Objects/RemoveObjectRoots took 00:00:00.0033258.

[Tanya-Solyanik]

@awaescher - thank you for the detailed repro case, it was very helpful. The fix for this issue is in the pipeline targeting the December patch Tuesday for VisualStudio 2022 17.4 release

[merriemcgaw]

@Shyam-Gupta will be taking a look at this in a few days. I’ll make sure it’s on his radar. @Olina-Zhang thanks for the confirmation link!