C / C++ / MFC

CString GetMachineName()
{
	DWORD dwsize = MAX_COMPUTERNAME_LENGTH + 1 ;
	char name[MAX_COMPUTERNAME_LENGTH + 1 ];
	if (!::GetComputerName(&name[0], &dwsize))
		throw E_FAIL;
	}
	CString strName(name);
	return strName;

}

class CMutexAccesor
{
  public:
    CMutexAccesor(LPCTSTR lpstrMutexName){
      res=(mutex=CreateMutex(NULL,FALSE,lpstrMutexName))!=NULL;
      if(res){
        // Wait up to 4 secs for locking
        res=WaitForSingleObject(mutex,4000)==WAIT_OBJECT_0;
        if(!res)CloseHandle(mutex);
      }
    }
    ~CMutexAccesor(){
      if(res){
        ReleaseMutex(mutex);
        CloseHandle(mutex);
      }
    }

    BOOL res;

  private:
    HANDLE mutex;
};

class CTester(prsSomeTable)
{
	UpdateDB()
	{
		CMutexAccessor *pMut;
		pMut = new CMutexAccessor();
		prs->Edit();
		prs->x = 2;
		prs->Update();
		delete pMut;
	}
};

class CTester(prsSomeTable)
{
	UpdateDB()
	{
		CMutexAccessor *pMut;

		prs->Edit();
		prs->x = 2;
		pMut = new CMutexAccessor();
		prs->Update();
		delete pMut;
	}
};

UpdateDB()
	{
		CMutexAccessor mut("MYONEANDONLYNAMENOONECAMETOFIGUREOUTBEFORE");
		prs->Edit();
		prs->x = 2;
		pMut = new CMutexAccessor();
		prs->Update();
	}

class CRequests : public CRecordset
{
public:
	CRequests(CDatabase* pDatabase = NULL);
	DECLARE_DYNAMIC(CRequests)

// Field/Param Data
	//{{AFX_FIELD(CRequests, CRecordset)
	long	m_ID;
	CString	m_SERVICE_TYPE;
clip for brevity
	//}}AFX_FIELD
	CMutexAccesor *pMutex;
#define DBMUTEX "AFX_REQUESTS_3B2738B5_A172_11D5_9FCB_00B0D081C96F"

// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CRequests)
	public:
	virtual CString GetDefaultConnect();    // Default connection string
	virtual CString GetDefaultSQL();    // Default SQL for Recordset
	virtual void DoFieldExchange(CFieldExchange* pFX);  // RFX support
	//}}AFX_VIRTUAL
	virtual void AddNew()
	{
		try 
		{
			pMutex = new CMutexAccesor(DBMUTEX);
			CRecordset::AddNew();
		}
		catch (CDBException *e)
		{
			if (pMutex)
			{
				if (pMutex) delete pMutex;
				pMutex = NULL;
			}
			throw e;
		}
		if (pMutex) delete pMutex;

	}

	virtual void Edit()
	{
		try
		{
			pMutex = new CMutexAccesor(DBMUTEX);
			CRecordset::Edit();
		}
		catch (CDBException *e)
		{
			if (pMutex)
			{
				if (pMutex) delete pMutex;
				pMutex = NULL;
			}
			throw e;
		}
		if (pMutex) delete pMutex;
	}

	virtual BOOL Update()
	{
		BOOL bRet;
		try
		{
			bRet = CRecordset::Update();
		}
		catch (CDBException *e)
		{
			delete pMutex;
			throw e;
		}
		delete pMutex;
		return bRet;
	}
	
	void AbandonUpdate()
	{
		if (pMutex) delete pMutex;
	}

};