求教一个最简单的MFC程序问题……

代码如下：
比着书抄下来的，但总是编译不通过。。。
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#include<afxwin.h>
class CHelloApp:public CWinApp
{
public:
virtual BOOL InitInstance();
};
CHelloApp theApp;
class CmainFrame:public CFrameWnd
{
public:
CMainFrame()
{
Create(NULL,"wod chuangkou",WS_OVERLAPPEDWINDOW,CRect(0,0,400,300));
}
protected:
afx_msg void OnLButtonDown(UINT nFlags,CPoint point);
DECLARE_MESSAGE_MAP()
};
BEGIN_MESSAGE_MAP(CMainFrame,CFrameWnd)
ON_WM_LBUTTONDOWN()
END_MESSAGE_MAP()
void CMainFrame::OnLButtonDown(UINT nFlags,CPoint point)
{
MessageBox("nihao,wod c world mfc","wenhou",0);
CFrameWnd::OnLButtonDown(nFlags,point);
}
BOOL CHelloApp::InitInstance()
{
m_pMainWnd=new CMainFrame();
m_pMainWnd->ShowWindow(m_nCmdShow);
m_pMainWnd->UpdateWindow();
return TRUE;
}