C++ / CLI cannot access protected member of base class - c++-cli

Question

I have this class:
ref class Wrapper {
protected:
Native *pn;
public:
Wrapper(int val) { pn = new Native( val ); }
};
Then I derive from it:
ref class DerivedWrapper : public Wrapper{
public:
DerivedWrapper(int val) {pn = new DerivedNative(val); }
}
The compiler complains:
error C2248 ‘ Wrapper::pn’ : cannot access private member declared in class ‘Wrapper’
The base class native pointer is clearly protected, and the derived class should have ready access to it. All my instincts tell me this should work. Is there something peculiar to ref classes?
I’m compiling with VS 2008 SP 1

Answer 1

The native type in your case has to have public or protected accessibility in the compiled assembly itself. There is a special make_public pragma directive that can promote the native type. Add this to the code:
#pragma make_public(Native)
The make_public pragma is documented at http://msdn.microsoft.com/en-us/library/ms235607.aspx

Answer 2

Consider initializing pn in a constructor of Wrapper, or you need to provide default constructor for your Wrapper. Don't forget 'public' in the ref class definition.
public ref class Wrapper {
protected:
Native *pn;
Wrapper(Native * fpn):pn(fpn)
{}
public:
Wrapper(int val) { pn = new Native( val ); }
};
ref class DerivedWrapper : public Wrapper{
public:
DerivedWrapper(int val):Wrapper(new DerivedNative(val)){}
};