How to load function from derived class from dll

Question

Dear all,
how to access extra function from derived class.
for Example
//==========================MyIShape.h
class CMyIShape
public:
CMyIShape(){};
virtual ~CMyIShape(){};
virtual void Fn_DrawMe(){};
// =========== this is ShapRectangle.dll
//==========================ShapRectangle .h
#include "MyIShape.h"
class DLL_API ShapRectangle :public CMyIShape
public:
ShapRectangle(){};
virtual ~ShapRectangle(){};
virtual void Fn_DrawMe(){/*something here */};
virtual void Fn_ChangeMe(){/*something here */};
__declspec (dllexport) CMyIShape* CreateShape()
// call the constructor of the actual implementation
CMyIShape * m_Obj = new ShapRectangle();
// return the created function
return m_Obj;
// =========== this is ShapCircle .dll
//==========================ShapCircle .h
#include "MyIShape.h"
class DLL_API ShapCircle :public CMyIShape
public:
ShapCircle(){};
virtual ~ShapCircle(){};
virtual void Fn_DrawMe(){/*something here */};
virtual void Fn_GetRadious(){/*something here */};
__declspec (dllexport) CMyIShape* CreateShape()
// call the constructor of the actual implementation
CMyIShape * m_Obj = new ShapCircle();
// return the created function
return m_Obj;
in exe there is no include header of of ShapCircle and ShapRectangle 
and from the exe i use LoadLibrary and GetProcAddress .
typedef CMyIShape* (*CREATE_OBJECT) ();
CMyIShape*xCls ;
//===================== from ShapeCircle.Dll
pReg=  (CREATE_OBJECT)GetProcAddress (hInst ,"CreateShape");
xCls = pReg();
now xCls give all access of base class. but how to get pointer of funciton Fn_GetRadious() or how to get access.
thanks in advance.

Answer 1

could you please tell me in detail. why so. or any reference for it. i love to read.
i don't know this is bad way.. but how? i would like to know.
I indicated in the second sentence. Classes can be implemented differently by different compilers. For example, the alignment of member variables may differ. Also there is the pitfall that a class may be allocated within the DLL but deallocated in the client
code. But the allocation/deallocation algorithms may differ across different compilers, and certainly between DEBUG and RELEASE mode. This means that you must ensure that if the DLL is compiled in Visual Studio 2010 / Debug mode, that the client code is also
compiled in Visual Studio 2010 / Debug mode. Otherwise your program will be subject to mysterious crashes.
is there any other way to archive same goal?
Of course. DLL functionality should be exposed as a set of functions that accept and return POD data types. "POD" means "plain-ole-data" such as long, wchar_t*, bool, etc. Don't pass pointers to classes. 
Obviously classes can be implemented within the DLL but they should be kept completely contained within the DLL. You might, for example, expose a function to allocate a class internally to the DLL and another function that can be called by the client code
to free the class. And of course you can define other functions that can be used by the client code to indirectly call the class's methods.
and why i need to give header file of ShapCircle and shapRectangle class, even i am not using in exe too. i though it is enough to give only MyIShape.h so with this any one can make new object.
Indeed you don't have to, if you only want to call the public properties and methods that are defined within MyIShape.h.