How to get a pointer to AFX_MODULE_STATE of a DLL?

Question

Our MFC-project is split into an exe and several dlls, which may also contain MFC-dialogs. For loading such a dialog, the dll contains an exported dll function. We have troubles loading the right resources for the dialog.

At the moment, the function looks like this:

extern "C" __declspec( dllexport ) int ShowDialog()
{
    HINSTANCE hInstOld = AfxGetResourceHandle();
    AfxSetResourceHandle(DXFDECDLL.hResource);
    CMyDllDialog dlg;
    AfxSetResourceHandle(hInstOld);
    dlg.DoModal();
    return 1;
}

It is working (most of the time), but seems to be bad. The function AfxSetResourceHandle sets the resource handle of the current AFX_MODULE_STATE and this module state is the one of the exe. If some other thread tries to load a string from the resource in the meantime, it will fail.

I think, we have to change the active module state, but I don't know how.

I have read the following article, but its guildlines fail. https://docs.microsoft.com/en-us/cpp/mfc/tn058-mfc-module-state-implementation?view=msvc-170

1. The AFX_MODULE_STATE does not seem to be changed automatically, if I load the DLL with LoadLibrary and calling the method via a function pointer. Do I need to edit the automatically generated DLLMain?
2. If I try to call AFX_MANAGE_STATE(AfxGetStaticModuleState()); in my function ShowDialog, I get a linker error LINK2005: "_DLLMain@12 is already defined in DXFDEC.obj"

---

Concerning the comment of @IInspectable, here is a minimal example, which generates a linker error. It is generated by the Visual Studio code generator. I have just added the function MyFunction

#include "pch.h"
#include "framework.h"
#include <afxwin.h>
#include <afxdllx.h>

static AFX_EXTENSION_MODULE MFCLibrary3DLL = { false, nullptr };

extern "C" int APIENTRY DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID lpReserved)
{
    UNREFERENCED_PARAMETER(lpReserved);

    if (dwReason == DLL_PROCESS_ATTACH)
    {
        if (!AfxInitExtensionModule(MFCLibrary3DLL, hInstance))
            return 0;

        new CDynLinkLibrary(MFCLibrary3DLL);
    }
    else if (dwReason == DLL_PROCESS_DETACH)
    {
        AfxTermExtensionModule(MFCLibrary3DLL);
    }
    return 1;   // OK
}

extern "C" __declspec(dllexport) int MyFunction()
{
    AFX_MANAGE_STATE(AfxGetStaticModuleState());
    return 0;
}