create dll and use it,only use very little thing!

!!!!!!!
1:use:
//func code.
void CAboutDlg::OnTestUseDll()
{
 typedef void (WINAPI * func)();
 HINSTANCE hmod;
 hmod = ::LoadLibrary ("firstDLL.dll");
 if(hmod==NULL)
 {
  AfxMessageBox("Fail");
 }
 func lpproc;
 lpproc = (func)GetProcAddress (hmod,"Show");
 if(lpproc!=(func)NULL)
  (*lpproc)();
 
 FreeLibrary(hmod);
}

!!!!!!!!!!
//2:sorce code,only add a dlg and in global add a declearion of func and implemention it.!
/////////////////////////////////////////////////////////////////////////////
// The one and only CFirstDLLApp object

CFirstDLLApp theApp;

//give the func that will can be used.

extern "C" __declspec(dllexport) void Show()
{
 AFX_MANAGE_STATE(AfxGetStaticModuleState());
 TestDlg test;
 test.DoModal ();
}

//and sorce dlg src
// TestDlg.cpp : implementation file
//

#include "stdafx.h"
#include "firstDLL.h"
#include "TestDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// TestDlg dialog

TestDlg::TestDlg(CWnd* pParent /*=NULL*/)
 : CDialog(TestDlg::IDD, pParent)
{
 //{{AFX_DATA_INIT(TestDlg)
  // NOTE: the ClassWizard will add member initialization here
 //}}AFX_DATA_INIT
}

void TestDlg::DoDataExchange(CDataExchange* pDX)
{
 CDialog::DoDataExchange(pDX);
 //{{AFX_DATA_MAP(TestDlg)
  // NOTE: the ClassWizard will add DDX and DDV calls here
 //}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(TestDlg, CDialog)
 //{{AFX_MSG_MAP(TestDlg)
 //}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// TestDlg message handlers

void TestDlg::OnCancel()
{
 // TODO: Add extra cleanup here
 
 CDialog::OnCancel();
}

void TestDlg::OnOK()
{
AfxMessageBox(" in dll 's dlg"); 
 CDialog::OnOK();
}