The app.config sample on this page shows a root node of <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">, but should have a <configuration> root node. I suspect this is a copy and paste typo from the app.manifest sample above it.

Edit: The following page has a correct app.config sample usage:https://docs.microsoft.com/en-us/dotnet/framework/configure-apps/file-schema/winforms/

Document Details

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• ID: 67438c9c-fecf-d5df-d381-93b519929711
• Version Independent ID: f1980646-43a3-6ecb-88cd-7dd2fab5c2ce
• Content:High DPI support - Windows Forms .NET Framework
• Content Source:dotnet-desktop-guide/framework/winforms/high-dpi-support-in-windows-forms.md
• Product:dotnet-framework
• Technology:dotnet-winforms
• GitHub Login:@adegeo
• Microsoft Alias:adegeo