public static class Test
{
    internal enum TestEnum
    {
        C = 0, D = 1
    }
    private class TestInner
    {
        internal enum TestInnerEnum
        {
            A = 0, B = 1
        }
    }

    public static void RunTest()
    {
        Console.Write(TestInner.TestInnerEnum.A);
    }
}