Can not use MFC standard classes in managed methods

[newwares]

There is a mixed managed and unmanaged c++ library: myclass.dll

#include <afxext.h>
#include <afx.h>
public __gc class MyClass1
{
public:
BOOL PrintBoundary(CDC* pdc, CPrintInfo* pInfo); //call some
unmanaged methods
};
A MFC Application(compiled with /clr and managed extension) will use
it:
#using "myclass.dll"

//...
CDC* pdc;
CPrintInfo* pinfo;
//...
#pragma push_macro("new")
#undef new
MyClass1* c1=new MyClass1;
#pragma pop_macro("new")
c1->PrintBoundary(pdc,pinfo);

I get some compiler error messages:
mfapp.cpp(52): error C3376: 'CDC' : type is inaccessible
mfapp.cpp(52): error C3377: 'myclass::MyClass1::PrintBoundary' :
cannot import method - a parameter type or the return type is
inaccessible

As I have so many classes using the MFC standard class, I cannot wrap
them one by one by deriving a public managed class.
Any suggestion is welcome. Thanks