How to make a MFC application to DLL? - c++

Question

I am new to MFC programming. I have a very simple MFC application that shows a plain dialog. I want to make a DLL that do the same as this piece of code.
The working dialog code looks like this:
class MyForm : public CDialog
{
public:
MyForm(CWnd* pParent = NULL) : CDialog(MyForm::IDD, pParent) {};
enum { IDD = DIALOG1 };
protected:
virtual void DoDataExchange(CDataExchange* pDX) { CDialog::DoDataExchange(pDX); };
virtual BOOL OnInitDialog()
{
CDialog::OnInitDialog();
return true;
}
public:
DECLARE_MESSAGE_MAP()
};
//Actural App
class MyApp: public CWinApp
{
public:
MyApp() {};
virtual BOOL InitInstance()
{
CWinApp::InitInstance();
MyForm dlg;
m_pMainWnd = &dlg;
INT_PTR nResponse = dlg.DoModal();
return false;
}
};
BEGIN_MESSAGE_MAP(MyForm, CDialog)
END_MESSAGE_MAP()
//start the app
MyApp theApp;
I use visual studio MFC DLL project to make a new DLL project. I make a separate *.h file to declare the dll class, and a *.cpp file to define the class.
This is the *.h file looks like:
//header file for dll project
#include "stdafx.h"
#include <afxwin.h>
#include "resource.h"
class CMyDllApp : public CDialog
{
public:
__declspec(dllexport) CMyDllApp();
enum { IDD = DLL_Dialog };
protected:
__declspec(dllexport) virtual void DoDataExchange(CDataExchange* pDX);
__declspec(dllexport) virtual BOOL OnInitDialog();
public:
__declspec(dllexport) afx_msg void myFunction();
DECLARE_MESSAGE_MAP()
};
//Actural App
class MyDllMain : public CWinApp
{
public:
__declspec(dllexport) MyDllMain() {};
__declspec(dllexport) virtual BOOL InitInstance();
};
Now I include the *.h file in my client application, but I don't know how to call the dll class correctly.
Even if I only include the *.h file and do not add any other code, the dialog of dll class just replace my client dialog, if have MyDllMain theApp; in the cpp file of dll project.
//in *.cpp of the dll project
...
MyDllMain theApp;
If I put this line in my client application, I just get a "Assertion Failed" error when running.
But if I don't put the line MyDllMain theApp; in dll project, how can I call my dll class when I want?