ActiveX

Overview
This code is meant to illustrate how to use COM in order to retrieve a list of all the registered ActiveX controls in your system. The demo application (see screen shot above) displays the names of all located ActiveX controls in a listbox.
Source Code

//Initialise COM libraries
CoInitialize (NULL);

//The Component Category Manager implemented by System implements
//this interface
ICatInformation *pCatInfo=NULL;

//Create an instance of standard Component Category Manager
HRESULT hr=CoCreateInstance (CLSID_StdComponentCategoriesMgr ,
                             NULL,
                             CLSCTX_INPROC_SERVER,
                             IID_ICatInformation ,
                             (void **)&pCatInfo);

//Increase ref count on interface
pCatInfo->AddRef ();

//IEnumGUID interface provides enumerator for enumerating through
//the collection of COM objects
IEnumGUID *pEnumGUID=NULL;

//We are intersted in finding out only controls so put CATID_Control
//in the array
CATID pcatidImpl[1];
CATID pcatidReqd[1];
pcatidImpl[0]=CATID_Control;

//Now enumerate the classes i.e. COM objects of this type.
pCatInfo->EnumClassesOfCategories (1,
                                   pcatidImpl,
                                   0,
                                   pcatidReqd ,
                                   &pEnumGUID);

//Enumerate as long as you get S_OK
CLSID clsid;

while( (hr= pEnumGUID->Next( 1, &clsid, NULL ))==S_OK )
{
 BSTR bstrClassName;   //Get the information of class

 //This is what MSDN says about the parameters
 /*-----------------------------------------------
 USERCLASSTYPE_FULL     The full type name of the class.
 USERCLASSTYPE_SHORT    A short name (maximum of 15 characters) that
                        is used for popup menus and the Links dialog
                        box.
 USERCLASSTYPE_APPNAME  The name of the application servicing the class
                        and is used in the Result text in dialog boxes.
 -----------------------------------------------*/
 OleRegGetUserType (clsid,USERCLASSTYPE_FULL,&bstrClassName);
 CString strControlName(bstrClassName);
 //Add string in our listbox
 m_list1.AddString (strControlName);
}

//we are done so now release the interface ptr
pCatInfo->Release ();

CoUninitialize ();

The program first intialises the COM libraries. Then it creates an instance of standard component category manager

HRESULT hr=CoCreateInstance(CLSID_StdComponentCategoriesMgr,
                            NULL,
                            CLSCTX_INPROC_SERVER,
                            IID_ICatInformation,
                            (void **)&pCatInfo);

IcatInformation interface provides the information about COM classes and categories. IEnumGUID interface provides enumerator for iterating through the collection of COM classes. Then we enumerate the controls with a call to EnumClassesOfCategories.As we are interested in only controls We fill the array with CATID_Control.Next we enumerate through the collection ,get the class name And put it in the listbox.