1、在应用程序类InitInstance()函数中判断是否已有一个应用程序实例正在运行。 BOOL CMutexApp::InitInstance() {        //创建命名信标对象。        HANDLE hSem=CreateSemaphore(NULL,1,1,"维新");        if(hSem)  //信标对象创建成功。        {               //信标对象已经存在，则程序已有一个实例在运行。               if(ERROR_ALREADY_EXISTS==GetLastError())               {                                       CloseHandle(hSem);      //关闭信号量句柄。   //获取桌面窗口的一个子窗口。                      HWND hWndPrev=::GetWindow(::GetDesktopWindow(),GW_CHILD);                          while(::IsWindow(hWndPrev))                      {                      //判断窗口是否有我们预先设置的标记，如有，则是我们寻找的窗口，并将它激活。                             if(::GetProp(hWndPrev,"维新"))                               {                             //如果主窗口已最小化，则恢复其大小。                                    if (::IsIconic(hWndPrev))                                               ::ShowWindow(hWndPrev,SW_RESTORE);                                      //将应用程序的主窗口激活。                                    ::SetForegroundWindow(hWndPrev);                                    return FALSE;                      //退出实例。                             }                             //继续寻找下一个窗口。                             hWndPrev = ::GetWindow(hWndPrev,GW_HWNDNEXT);                      }                                          AfxMessageBox("已有一个实例在运行，但找不到它的主窗口！");               }        }        else        {               AfxMessageBox("创建信标对象失败，程序退出！");               return FALSE;        }          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          // Change the registry key under which our settings are stored.        // TODO: You should modify this string to be something appropriate        // such as the name of your company or organization.        SetRegistryKey(_T("Local AppWizard-Generated Applications"));          LoadStdProfileSettings();  // Load standard INI file options (including MRU)          // Register the application's document templates.  Document templates        //  serve as the connection between documents, frame windows and views.          CSingleDocTemplate* pDocTemplate;        pDocTemplate = new CSingleDocTemplate(               IDR_MAINFRAME,               RUNTIME_CLASS(CMutexDoc),               RUNTIME_CLASS(CMainFrame),       // main SDI frame window               RUNTIME_CLASS(CMutexView));        AddDocTemplate(pDocTemplate);          // Parse command line for standard shell commands, DDE, file open        CCommandLineInfo cmdInfo;        ParseCommandLine(cmdInfo);          // Dispatch commands specified on the command line        if (!ProcessShellCommand(cmdInfo))               return FALSE;          // The one and only window has been initialized, so show and update it.        m_pMainWnd->ShowWindow(SW_SHOW);        m_pMainWnd->UpdateWindow();          return TRUE; } 2、在框架类的OnCreate()函数中设置查找标记。 int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct) {        if (CFrameWnd::OnCreate(lpCreateStruct) == -1)               return -1;              if (!m_wndToolBar.CreateEx(this, TBSTYLE_FLAT, WS_CHILD | WS_VISIBLE | CBRS_TOP               | CBRS_GRIPPER | CBRS_TOOLTIPS | CBRS_FLYBY | CBRS_SIZE_DYNAMIC) ||               !m_wndToolBar.LoadToolBar(IDR_MAINFRAME))        {               TRACE0("Failed to create toolbar/n");               return -1;      // fail to create        }          if (!m_wndStatusBar.Create(this) ||               !m_wndStatusBar.SetIndicators(indicators,                 sizeof(indicators)/sizeof(UINT)))        {               TRACE0("Failed to create status bar/n");               return -1;      // fail to create        }          // TODO: Delete these three lines if you don't want the toolbar to        //  be dockable          m_wndToolBar.EnableDocking(CBRS_ALIGN_ANY);        EnableDocking(CBRS_ALIGN_ANY);        DockControlBar(&m_wndToolBar);                //设置查找标记。        ::SetProp(m_hWnd,"维新",(HANDLE)1);          return 0; } 3、在程序退出是删除设置的标记，在框架类中响应WM_DESTROY消息，进行处理。 void CMainFrame::OnDestroy() {        CFrameWnd::OnDestroy();              // TODO: Add your message handler code here        //删除所设置的标记。        ::RemoveProp(m_hWnd,"维新"); } 至此，使应用程序只运行一个实例的功能就完成了。