__declspec(dllexport) and static lib

I have a static library project and a exe project. The exe project uses the static lib. In my static lib I have several classes split into seperate .h and .cpp files. However the project is that some of the classes require __declspec(dllexport) and some don't. All of the classes are used in the exe in a similar fasion. If I don't put __declspec(dllexport) on the classes that some reason require it I get the error:

error LNK2001: unresolved external symbol "public: __thiscall EffectObjectBase::operator char const *(void)" (??BEffectObjectBase@@QAEPBDXZ) Main.obj

Of course if I don't use that class in the exe the error doesn't exist. The class looks like this:

Code:

---

class EffectObjectBase
{
friend class Effect;
friend class EffectTechnique;

protected:
        Effect* effect;
        D3DXHANDLE handle;


public:
        EffectObjectBase();
        __forceinline Effect* GetEffect();
        __forceinline D3DXHANDLE GetHandle();

        __forceinline operator D3DXHANDLE();
};

---

Just a note, both Effect and EffectTechnique also require __declspec(dllexport).

Does anyone have an idea why some of the classes require it and the others don't?