void CRuingcarView::OnDraw(CDC* pDC)
{
    CRuingcarDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
   

    if(m_vchang==0&&m_vkuan==0)
     if(dlg.DoModal()==IDOK)
        {m_vchang=dlg.m_chang;
       m_vkuan=dlg.m_kuan;
        }
    // TODO: add draw code for native data here
    CClientDC dc(this);
    dc.Rectangle(10,10,m_vchang,m_vkuan);
    CBitmap Bitmap;
    Bitmap.LoadBitmap(IDB_BITMAP1);
    CDC MemDC;
    MemDC.CreateCompatibleDC(pDC);
    CBitmap*OldBitmap=MemDC.SelectObject(&Bitmap);
    BITMAP bm;
    Bitmap.GetBitmap(&bm);
    pDC->BitBlt(x,y,bm.bmWidth,bm.bmHeight,&MemDC,0,0,SRCCOPY);
    pDC->SelectObject(OldBitmap);

 

}

错误
:\VC++\Ruingcar\RuingcarView.cpp(64) : error C2065: 'dlg' : undeclared identifier
F:\VC++\Ruingcar\RuingcarView.cpp(64) : error C2228: left of '.DoModal' must have class/struct/union type
F:\VC++\Ruingcar\RuingcarView.cpp(65) : error C2228: left of '.m_chang' must have class/struct/union type
F:\VC++\Ruingcar\RuingcarView.cpp(66) : error C2228: left of '.m_kuan' must have class/struct/union type
Error executing cl.exe.

程序

error C2065: 'dlg' : undeclared identifier

很明确啦，没有定义