As SA said, your code did not use any C++/CLI and what you pasted will not even compile. Here's the fixed version that will compile, although it has nothing to do with C++/CLI:
class B{};
class A
{
protected :
B b;
int m;
};
private class C : A
{
public:
void method();
};
void C::method()
{
A::m;
}