* enable: The nullable annotation context is enabled. The nullable warning context is enabled. * Variables of a reference type, string for example, are non-nullable. All nullability warnings are enabled. * warnings: The nullable annotation context is disabled. The nullable warning context is enabled. * Variables of a reference type are oblivious. All nullability warnings are enabled. * annotations: The nullable annotation context is enabled. The nullable warning context is disabled. * Variables of a reference type, string for example, are non-nullable. All nullability warnings are disabled. * disable: The nullable annotation context is disabled. The nullable warning context is disabled. * Variables of a reference type are oblivious, just like earlier versions of C#. All nullability warnings are disabled.
