CoCreateInstance

Creates a single uninitialized object of the class associated with a specified CLSID. Call CoCreateInstance when you want to create only one object on the local system. To create a single object on a remote system, call CoCreateInstanceEx. To create multiple objects based on a single CLSID, refer to the CoGetClassObject function.

STDAPI CoCreateInstance(

REFCLSID rclsid,

//Class identifier (CLSID) of the object

LPUNKNOWN pUnkOuter,

//Pointer to whether object is or isn’t part of an aggregate

DWORD dwClsContext,

//Context for running executable code

REFIID riid,

//Reference to the identifier of the interface

LPVOID * ppv

//Indirect pointer to requested interface

);

Parameters

rclsid: [in] CLSID associated with the data and code that will be used to create the object.
pUnkOuter: [in] If NULL, indicates that the object is not being created as part of an aggregate. If non-NULL, pointer to the aggregate object’s IUnknown interface (the controlling IUnknown).
dwClsContext: [in] Context in which the code that manages the newly created object will run. The values are taken from the enumeration CLSCTX.
riid: [in] Reference to the identifier of the interface to be used to communicate with the object.
ppv: [out] Indirect pointer to the requested interface.

Return Values

S_OK: An instance of the specified object class was successfully created.
REGDB_E_CLASSNOTREG: A specified class is not registered in the registration database. Also can indicate that the type of server you requested in the CLSCTX enumeration is not registered or the values for the server types in the registry are corrupt.
CLASS_E_NOAGGREGATION: This class cannot be created as part of an aggregate.

Remarks

The CoCreateInstance helper function provides a convenient shortcut by connecting to the class object associated with the specified CLSID, creating an uninitialized instance, and releasing the class object. As such, it encapsulates the following functionality:

CoGetClassObject(rclsid, dwClsContext, NULL, IID_IClassFactory, &pCF); 
hresult = pCF->CreateInstance(pUnkOuter, riid, ppvObj) 
pCF->Release();

It is convenient to use CoCreateInstance when you need to create only a single instance of an object on the local machine. If you are creating an instance on remote machine, call CoCreateInstanceEx. When you are creating multiple instances, it is more efficient to obtain a pointer to the class object’s IClassFactory interface and use its methods as needed. In the latter case, you should use the CoGetClassObject function.

In the CLSCTX enumeration, you can specify the type of server used to manage the object. The constants can be CLSCTX_INPROC_SERVER, CLSTCTX_INPROC_HANDLER, CLSCTX_LOCAL_SERVER, or any combination of these values. The constant CLSCTX_ALL is defined as the combination of all three. For more information about the use of one or a combination of these constants, refer to CLSCTX.

REFCLSID rclsid,	//Class identifier (CLSID) of the object
LPUNKNOWN pUnkOuter,	//Pointer to whether object is or isn’t part of an aggregate
DWORD dwClsContext,	//Context for running executable code
REFIID riid,	//Reference to the identifier of the interface
LPVOID * ppv	//Indirect pointer to requested interface
);