I have a

• Class library created using C# and Visual Studio 2022 ElabAddInMetricsDb
• Windows forms app (.NET Framework) created using C# and Visual Studio 2022 ElabAddInMetricsDbDemo

In VS for the class library, I configured the Target Framework:

In VS for the Windows forms app (.Net Framework), I configured the Target Framework:

In the Windows forms app (.Net Framework), I added a ref to the class library DLL:

When I build and the execute the Windows forms app , I get:

So, am I missing runtime version 8 software, or, is there a mismatch between my class library and Windows App, or something else?

Note: See below. Control Panel -> Programs for my dev machine shows .NET SDK 8

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FYI

My development machine is running Windows 10 Enterprise, 22H2, 64 bit and Visual Studio 2022 Enterprise.

Control Panel (filter = .net) shows:

C:WindowsMicrosoft.NetFramework64 shows: