cheating.cs

public class AlmostFriendClass
{
    interface INestedClass
    {
        void CallMethod(AlmostFriendClass afc);
    }

    public class NestedClass : INestedClass
    {
        void INestedClass.CallMethod(AlmostFriendClass afc)
        {
            SomeMethod();
            afc.BaseClassPrivateMethod();
        }

        protected virtual void SomeMethod()
        {
                
        }
    }

    private void TestMethod()
    {
        INestedClass nc = new NestedClass();
        nc.CallMethod(this);
    }

    private void BaseClassPrivateMethod()
    {
            
    }
}