Each thread that wants to use the «COM library» must call CoInitializeEx (or CoInitialize) to initialize it.
The only function of the COM library that can be used without initializing it is CoGetMalloc (which returns a pointer to the default OLE task memory allocator).
Parameters
CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);
CoInitializeEx(NULL, COINIT_MULTITHREADED);
lpReserved
Always NULL
dwCoInit
The value of dwCoInit (the 2nd parameter) specifes the thread's concurrency model (See also COM Apartments).
Return value
The function returns one of
S_OK
S_FALSE
The «COM library» is already initialized on this thread
RPC_E_CHANGED_MODE
The thread already called CoInitializeEx with a different concurrency model.
CoInitialize
CoInitialize provides the same functionality as CoInitializeEx, yet without the dwCoInit parameter.
With CoInitialize, the concurrency model is set to single-threaded apartment (STA).
Windows Runtime
When using the Windows Runtime, Windows::Foundation::Initialize must be used instead of CoInitializeEx.