What are the alternatives to dll registration for ActiveX

Question

An application I have recently started work on has to register two dll's, "because of ActiveX".

This makes it difficult to have multiple version of the application present on your machine - say the installed product version, and Debug and Release versions of the latest development sources.

What are the alternatives to registration for ActiveX.

Answer 1

If your application loads the ActiveX objects, there are a couple of options. The first option if you are using XP or newer, it to use a Registration-Free COM with a Manifest file as explained on MSDN. The idea is to declare your COM (ActiveX) components in a manifest file instead of the registry. So for MyApp.exe, create MyApp.exe.manifest with the following (using your DLL file name and CLSID):

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <assemblyIdentity type="win32" name="MyApp_ActiveX" version="1.0.0.1" 
        processorArchitecture="x86" publicKeyToken="0000000000000000" />

  <file name="MyActiveX.dll">
    <comClass clsid="{0000000-0000-0000-0000-000000000000}" threadingModel="Both" />
  </file>
</assembly>

The other option as DougN mentioned is to roll your own CoCreateInstance() to create the object. The following C++ (plus ATL) code should do it (going from memory so double check the code):

typedef int (__stdcall *LPDLLGETCLASSOBJECT)(REFCLSID, REFIID, void**);

// LoadInterface() - Load COM Interface from DLL without using registry.
//
// USAGE:   
//   HMODULE hModule = 0;
//   CComPtr<IMyActiveX> pActiveX;
//   if(SUCCEEDED(LoadInterface("C:\\Debug\\MyActiveX.dll", CLSID_MyActiveX, IID_IMyActiveX, (void**)&pActiveX, &hModule)))
//   {
//      // TODO: use pActiveX
// 
//      // caller must call FreeLibrary(hModule) when done
//      pActiveX = 0;
//      FreeLibrary(hModule); 
//   }
//
HRESULT LoadInterface(LPCTSTR pDllPath, REFCLSID rClsid, REFIID riid, LPVOID* ppv, HMODULE *pModule)
{
    if(pModule == 0 || ppv == 0) return E_POINTER;
    HMODULE hModule = LoadLibrary(pDllPath);
    if(hModule == 0) return E_FAIL;

    HREUSLT hr = E_POINTER;
    CComPtr<IClassFactory> classFactory;
    LPDLLGETCLASSOBJECT pGetClassObject = (LPDLLGETCLASSOBJECT)GetProcAddress(hModule, "DllGetClassObject");
    if(pGetClassObject)
    {
        hr = pGetClassObject(rClsid, IID_IClassFactory, (void**)&classFactory);
        if(SUCCEEDED(hr))
        {
            hr = classFactory->CreateInstance(0, riid, (void**)ppv);
            if(SUCCEEDED(hr))
            {
                *pModule = hModule;
                return S_OK;
            }
        }
    }

    // unload library on error
    if(hModule)  
    {
        FreeLibrary(hModule);
    }
    return hr;
 }