原始碼如下：

#pragma once



#define  DECLARE_SinglePrj   SinglePrj* SinglePrj::m_pSinglePrj = NULL;



#define  SinglePrj_InitInstance(szPropName)    SinglePrj *pSinglePrj = SinglePrj::GetInstance();\
if (NULL != pSinglePrj)\
if(!pSinglePrj->InitInstance(szPropName)) return FALSE;




#define SinglePrj_OnInitDialog    SinglePrj *pSinglePrj = SinglePrj::GetInstance(); \
if (NULL != pSinglePrj)  pSinglePrj->OnInitDialog(m_hWnd);




class SinglePrj
{
public:
static SinglePrj *m_pSinglePrj;
static SinglePrj *GetInstance()
{
if (NULL == m_pSinglePrj) m_pSinglePrj = new SinglePrj();

return m_pSinglePrj;
}


bool InitInstance(CString   szPropName)
{
m_szPropName = szPropName;
m_hValue = (HANDLE)1;




HWND oldHWnd = NULL;
EnumWindows(EnumWndProc,(LPARAM)&oldHWnd);


if (NULL == oldHWnd) return true;



::ShowWindow(oldHWnd,SW_SHOW);
::SetForegroundWindow(oldHWnd);
return false;
}
void OnInitDialog(HWND hwnd)
{
SetProp(hwnd,m_szPropName,m_hValue);
}
private:
static BOOL CALLBACK EnumWndProc(HWND hwnd,LPARAM lParam)
{
SinglePrj * pSinglePrj = GetInstance();
if (NULL == pSinglePrj) return false;

HANDLE h = GetProp(hwnd,pSinglePrj->m_szPropName);
if( h == pSinglePrj->m_hValue)
{
*(HWND*)lParam = hwnd;
return false;
}


return true;
}
private:
SinglePrj(){}
CString   m_szPropName;
HANDLE   m_hValue;
};

使用方法：

以程式名為 _T("Test") 為例

1.任意cpp中宣告巨集

DECLARE_SinglePrj

2.程式初始化函式中宣告巨集：

SinglePrj_InitInstance( _T("Test") )

2.窗體初始化函式中宣告巨集：

SinglePrj_OnInitDialog