// COUNTER4.cpp : Defines the class behaviors for the application.
//

#include "stdafx.h"
#include "COUNTER4.h"
#include "COUNTER4Dlg.h"

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

/////////////////////////////////////////////////////////////////////////////
// CCOUNTER4App

BEGIN_MESSAGE_MAP(CCOUNTER4App, CWinApp)
    //{{AFX_MSG_MAP(CCOUNTER4App)
        // NOTE - the ClassWizard will add and remove mapping macros here.
        //    DO NOT EDIT what you see in these blocks of generated code!
    //}}AFX_MSG
    ON_COMMAND(ID_HELP, CWinApp::OnHelp)
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CCOUNTER4App construction

CCOUNTER4App::CCOUNTER4App()
{
    // TODO: add construction code here,

    // Place all significant initialization in InitInstance
}

/////////////////////////////////////////////////////////////////////////////
// The one and only CCOUNTER4App object

CCOUNTER4App theApp;

/////////////////////////////////////////////////////////////////////////////
// CCOUNTER4App initialization

BOOL CCOUNTER4App::InitInstance()
{
    AfxEnableControlContainer();

    // Standard initialization
    // If you are not using these features and wish to reduce the size
    //  of your final executable, you should remove from the following
    //  the specific initialization routines you do not need.

#ifdef _AFXDLL
    Enable3dControls();            // Call this when using MFC in a shared DLL
#else
    Enable3dControlsStatic();    // Call this when linking to MFC statically
#endif

    CCOUNTER4Dlg dlg;
    m_pMainWnd = &dlg;
    int nResponse = dlg.DoModal();
    if (nResponse == IDOK)
    {
        // TODO: Place code here to handle when the dialog is
        //  dismissed with OK
    }
    else if (nResponse == IDCANCEL)
    {
        // TODO: Place code here to handle when the dialog is
        //  dismissed with Cancel
    }

    // Since the dialog has been closed, return FALSE so that we exit the
    //  application, rather than start the application's message pump.
    return FALSE;
}
Linking...
COUNTER4.obj : error LNK2001: unresolved external symbol "public: __thiscall CCOUNTER4Dlg::CCOUNTER4Dlg(class CWnd *)" (??0CCOUNTER4Dlg@@QAE@PAVCWnd@@@Z)
Debug/COUNTER4.exe : fatal error LNK1120: 1 unresolved externals
unresolved external symbol 表示不确定的外部符号

刚学VC++，在网上查了一晚上也没改对。我就按照书上的定义的project,可关闭程序后再运行就出现这样的错误啦。为什么出现这样的错误啊？怎么改啊？急求

include CCOUNTER4Dlg对应的头文件是什么样的，在哪能看到啊？如果没有需要重写一个吗 ？请再指点下