Open the attached solution (.sln file is in the folder myWinFormApp) in VS 2019 (it has errors in the code) and try to open Form1.prg in the designer, VS shows this error dialog:
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Microsoft Visual Studio
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The service Microsoft.VisualStudio.Shell.Interop.ISelectionContainer already exists in the service container.
Parameter name: serviceType
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OK
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Open the attached solution (.sln file is in the folder myWinFormApp) in VS 2019 (it has errors in the code) and try to open Form1.prg in the designer, VS shows this error dialog:
test.zip