Question

What the diffrence between this code:

::EnterCriticalSection( &m_CriticalSection );
//...
::LeaveCriticalSection( &m_CriticalSection );

and the code:

static CCriticalSection cs;
cs.Lock();
//...
cs.UnLock();

Answer 1

No difference practically. CCriticalSection is the only syntatic sugar of the former. It internally uses EnterCriticalSection and LeaveCriticalSection!

EnterCriticalSection and LeaveCriticalSection are low-level win32 APIs, while CCriticalSection is a MFC class which wraps these functionalities. It has a member data of type CRITICAL_SECTION which is used by the APIs.

MSDN says,

The functionality of the
CCriticalSection class is provided by
an actual Win32 CRITICAL_SECTION
object.