InternalsVisibleTo is not working for wpf application

I have the [assembly:InternalsVisibleTo("GuiAssembly")] set in the other assembly but when wpf binding occurs on a class that lives in the other assembly, it throws an exception because of the property in that class be开发者_如何学运维ing internal.

I know this works with other applications but not sure why it is not working with this particular WPF app.

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I'm pretty sure that everything that WPF binds to needs to be public.