How do I free SQLServerCE's COM instance from the current running process?

Question

It's been a while since I touched COM so be nice ;) This is under WindowsCE 5.0 with SQLServerCE 2.0.

After calling this to load SQLServerCE 2.0 : -

IDBInitialize *pIDBInitialize = NULL;
CoCreateInstance(CLSID_SQLSERVERCE_2_0, NULL, CLSCTX_INPROC_SERVER, IID_IDBInitialize, (void**)&pIDBInitialize);

Module load occurs for SSCE20.dll which obviously loads the SQLServerCE engine into the process space.

What I don't understand is if I do this immediately after :-

pIDBInitialize->Release();

I don't see a dll module unload, so that SSCE20.dll (and friends) are still loaded into my process.

Now I tried CoFreeUnusedLibraries() which I figure forces COM to purge any unused libraries, but it doesn't seem to do the trick.

At runtime I want to be able to completely unload the SQLServerCE 2.0 dll from the process to streamline an upgrade to 3.5SP1.

I suspect this has something to do with the shared dll model that Microsoft use under WindowsCE... but, I might be wrong :)

Thanks in advance,

David.

Answer 1

I think CoFreeUnusedLibraries has been stubbed out in later versions of Windows (XP and forward, if I recall correctly). That is, it doesn't do anything.

A KB article mentions undue delays when calling the function, to minimize the risk that one thread forces unload of a DLL that another is concurrently attempting to create an instance from.

It could be that they weren't happy with the delayed unload (I suppose it still presents a possible race condition), and decided to remove the functionality entirely.

You could try calling CoUninitialize and see if that forces an unload.