Simple DLL giving me weird compile errors

I am creating my 1st DLL. I have just a singleton class & a LRESULT CALLBACK function that I will create in the DLL & import into one of my projects. My MSVC++ project architecture consists of the DLLMain.cpp file(unaltered), a header file that defines the singleton class & LRESULT function & a cpp file that implements the LRESULT function.

My Problem: the project is not compiling. I have 2 compile errors that I dont understand whats exactly wrong & how to fix it.

1>c:\users\testcreatedll\dlltest.h(15): error C2059: syntax error : '__declspec(dllexport)'

1>c:\users\testcreatedll\dlltest.h(39): error C2065: 'TestWndProc' : undeclared identifier

My header file:

#ifndef DLLTEST_H
#define DLLTEST_H

#include <windows.h>

// This is from a tutorial I am following
#ifdef _CLASSINDLL
#define CLASSINDLL_CLASS_DECL __declspec(dllexport)
#else
#define CLASSINDLL_CLASS_DECL __declspec(dllimport)
#endif

namespace MyTest
{
    LRESULT CALLBACK CLASSINDLL_CLASS_DECL TestWndProc( HWND hwnd, UINT msg, LPARAM lParam, WPARAM wParam );

    class CLASSINDLL_CLASS_DECL TestClass
    {
        // Singleton class
        public:
            static bool testStaticVar;

            static TestClass* getInstance()
            {
                if ( instance == NULL ) { instance = new TestClass(); }
                return instance;
            }

            void add()
            {
                myMember++;
            }

        private:
            static TestClass* instance;
            WNDPROC myProc;
            int myMember;

            TestClass() : myMember(0) { myProc = (WNDPROC)&TestWndProc; }
            ~TestClass()              {}

    };
}

#endif // DLLTEST_H

My cpp file:

#include "stdafx.h"
#include "DLLTest.h"

namespace MyTest
{
    // Create/Initialise? Class Static variables
    bool TestClass::testStaticVar = false;
    TestClass* TestClass::instance 开发者_运维技巧= NULL;

    LRESULT CALLBACK TestWndProc( HWND hwnd, UINT msg, LPARAM lParam, WPARAM wParam )
    {
        switch (msg)
        {
            case WM_CREATE:
            {

            }
            break;
            default:
            break;
        }

        return DefWindowProc(hwnd, msg, wParam, lParam);
    }

}

C++ compilers can be very picky about the order in which you declare the calling convention and storage-class information(export visibily with __declspec). AFAIK, VC++ needs the calling convention to appear after the storage-class. For example:

namespace MyTest
{
  LRESULT CLASSINDLL_CLASS_DECL CALLBACK TestWndProc( HWND hwnd, UINT msg, LPARAM lParam, WPARAM wParam );

  // ...
}

C++ Builder 2007 and MinGW-GCC-4.5.2, on the other-hand, doesn't care about this -- both forms are accepted.