VS2022 Designer not working with inherited .Net 6.0 Form

Question

Is there anything special I need to do in .Net 6.0 to allow VS2022 to display a C# Form that inherits from a class in a DLL?

I have an existing suite of C# applications/libraries in .Net Framework that I'm looking to convert to .Net 6 (and from 32-bit to 64-bit at the same time). I've got all the libraries compiled and working with .Net6 but when I try to create a new Form using the .Net 6 version of the DLL the VS2022 Designer just shows an error "The Designer could not be shown for this file because none of the classes within it can be designed". The program runs under debug in VS2022 and as a stand-alone .exe when published, so I'm positive everything is setup correctly reference/platform-wise, I just can't edit the Form in VS2022's Designer.

The identical code works when both the Project and referenced DLL are .Net Framework 4.72 (32-bit), it's only when I create it as a .Net 6.0 project that the Designer won't display. I've tried building the DLL as x86, x64 and Any CPU but it always gives the same error when I try to edit the Form.

Is there some extra step required to have VS2022's Designer work with .Net 6.0 DLLs?

Possibly related I can't get the Toolbox to display the .Net6.0 DLL's custom controls either - it works immediately with the .Net Framework DLL.

Answer 1

Hi @Toby Chamberlain ,
It might be a bug and is under Investigation.
Please check the following thread.
https://developercommunity.visualstudio.com/t/1740-NET6-WinForms-designer-regress/10198799

Best Regards.
Jiachen Li

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