How to determine if a object type is a built in system type

Question

I am writing a simple List to CSV converter. My converter checks the all the t\'s in List and grabs all public properties and places them

Answer 1

Given the caveats surrounding the existing answers, I am going to suggest a Windows only solution:

public static class TypeExt {
    public static bool IsBuiltin(this Type aType) => new[] { "/dotnet/shared/microsoft", "/windows/microsoft.net" }.Any(p => aType.Assembly.CodeBase.ToLowerInvariant().Contains(p));
}

Presumably there is a similar path on other supported operating systems.