Answer / revanth

BOOL CSampleApp::InitInstance()
{
// InitCommonControlsEx() is required on Windows XP
if an application
// manifest specifies use of ComCtl32.dll version 6
or later to enable
// visual styles. Otherwise, any window creation
will fail.
INITCOMMONCONTROLSEX InitCtrls;
InitCtrls.dwSize = sizeof(InitCtrls);
// Set this to include all the common control
classes you want to use
// in your application.
InitCtrls.dwICC = ICC_WIN95_CLASSES;
InitCommonControlsEx(&InitCtrls);

CWinApp::InitInstance();

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
// 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"));

if(NULL != ::CreateMutex(NULL, TRUE, _T
("CSingleInstanceApp")))
{
long dwError = ::GetLastError();
if(dwError == ERROR_ALREADY_EXISTS)
return false;
}

CSampleDlg dlg;
m_pMainWnd = &dlg;
INT_PTR nResponse = dlg.DoModal();
if (nResponse == IDOK)
{
// TODO: Place code here to handle when the
dialog is
// dismissed with OK
}
else if (nResponse == IDCANCEL)
{
// TODO: Place code here to handle when the
dialog is
// dismissed with Cancel
}

// Since the dialog has been closed, return FALSE
so that we exit the
// application, rather than start the
application's message pump.
return FALSE;
}

Answer / rajaram b

if(NULL != ::CreateMutex(NULL, TRUE,
_T("CSingleInstanceApp")))
{
long dwError = ::GetLastError();
if(dwError == ERROR_ALREADY_EXISTS)
EndDialog(IDOK);
}

Paste the above code snippet inside the "InitInstance"
function.

Answer / phaniram

if(NULL != ::CreateMutex(NULL, FALSE,_T
("CSingleInstanceApp")))
{
long dwError = ::GetLastError();
if(dwError == ERROR_ALREADY_EXISTS)
EndDialog(NULL,IDOK);
else
{
CDlgMutexDlg dlg;
m_pMainWnd = &dlg;
nResponse = dlg.DoModal();
}
}

Answer / sreekanth

A: You need to create a named mutex semaphore when you
start your application. When the second one starts it tries
to get access to the mutex but will fail...


Code:
// app.h
class CYourApp : public CWinApp
{
...

private:
HANDLE hMutex;
};

// app.cpp
BOOL CYourApp::InitInstance()
{
// Create mutex
hMutex = ::CreateMutex(NULL, TRUE, "GlobalMutex");

switch(::GetLastError())
{
case ERROR_SUCCESS:
// Mutex created successfully. There is no instance
running
break;

case ERROR_ALREADY_EXISTS:
// Mutex already exists so there is a running
instance of our app.
return FALSE;

default:
// Failed to create mutex by unknown reason
return FALSE;
}
}

Answer / harini

Write the constructor of the dialog in private of the class by making the class as single instance class.

Answer / krishna

Try this....

//...
BOOL CWinAppEx::EnableTokenPrivilege( LPCTSTR
lpszSystemName,
BOOL
bEnable /*TRUE*/ )
{
ASSERT( lpszSystemName != NULL );
BOOL bRetVal = FALSE;

if( ::GetVersion() < 0x80000000 ) // NT40/2K/XP //
afxData ???
{
HANDLE hToken = NULL;
if( ::OpenProcessToken( ::GetCurrentProcess(),
TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
&hToken ) )
{
TOKEN_PRIVILEGES tp = { 0 };
if( ::LookupPrivilegeValue( NULL,
lpszSystemName, &tp.Privileges[0].Luid ) )
{
tp.PrivilegeCount = 1;
tp.Privileges[0].Attributes = ( bEnable ?
SE_PRIVILEGE_ENABLED : 0 );


// To determine whether the function
adjusted all of the
// specified privileges, call GetLastError:

if( ::AdjustTokenPrivileges( hToken, FALSE,
&tp,
sizeof( TOKEN_PRIVILEGES ),
(PTOKEN_PRIVILEGES)NULL, NULL ) )
{
bRetVal = ( ::GetLastError() ==
ERROR_SUCCESS );
}
}
::CloseHandle( hToken );
}
}

return bRetVal;
}
//...

Answer / praveer

Hi,
i wrote the code as you told still its not
working,here is my code,please have a look
/////////////////////////////////////////////////////////////
BOOL CDlgApp::InitInstance()
{
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


if(NULL != ::CreateMutex(NULL, TRUE,_T("CSingleInstanceApp")))
{
long dwError = ::GetLastError();
if(dwError == ERROR_ALREADY_EXISTS)
EndDialog(NULL,IDOK);
}

CDlgDlg dlg;
m_pMainWnd = &dlg;
int nResponse = dlg.DoModal();




if (nResponse == IDOK)
{
// TODO: Place code here to handle when the dialog is
// dismissed with OK
}
else if (nResponse == IDCANCEL)
{
// TODO: Place code here to handle when the dialog is
// dismissed with Cancel
}

// Since the dialog has been closed, return FALSE so that
we exit the
// application, rather than start the application's
message pump.

return FALSE;
}
////////////////////////////////

What are the special requirements for dialog box resources used in a form view?

2 Answers  

What is the use of UpdateData funciton ?

7 Answers  

What is serialization ?which function is responsible for serializing data ?

5 Answers  

How WM_PAINT message gets called in MFC,please explain it . a)Who calls the WM_PAINT message? b)When it gets called? c)how it comes to message queue? Please Explain it

8 Answers  

if both base and derived class have the constructors if i create an object for derive class which class constructor is executed first

10 Answers   Siemens, Symphony,

Will there be any difference in the image buffer size if it is loaded in from CString to LPTSTR using GetBuffer()? lptstr = string.GetBuffer(0);

2 Answers  

What is the use of CCmdTarget ?

4 Answers  

Tell me about different kinds of synchranization objects ?

6 Answers  

How to handle dynamic menus in MFC?

3 Answers   HCL,

What is the base class for most MFC classes?

7 Answers   CMC, Siemens,

How we can findout Memoryleaks, In what way it can be avoided

6 Answers   Infosys,

Tell me the different controls in MFC ?

5 Answers