Trigger deletion of Outlook email attachment using VSTO AddIn from VC++ app - c++

Question

I am attempting to delete an email in Outlook from a VC++ app. I have an Outlook Addin that is loading in Outlook and registered with the system. The VC++ app to trigger the deletion of the email makes a call to CoCreateInstance() and returns successfully.
HRESULT hr;
IFoo* pISL;
CoInitialize(NULL);
LPOLESTR lpoleStr;
StringFromCLSID(__uuidof(Foo), &lpoleStr);
hr = CoCreateInstance(
__uuidof(Foo), // CLSID of coclass
NULL, // not used - aggregation
CLSCTX_INPROC_SERVER | CLSCTX_INPROC_HANDLER | CLSCTX_LOCAL_SERVER, // type of server
__uuidof(IFoo), // IID of interface
(void**)&pISL); // Pointer to our interface pointer
if (SUCCEEDED(hr))
{
//fire event
BSTR bstr = SysAllocString(params->szObjectPath);
pISL->FooMethod(bstr);
pISL->Release();
SysFreeString(bstr);
}
else
{
// Couldn't create the COM object. hr holds the error code.
}
CoUninitialize();
I am then using the COM object returned to call the methods in the COM interface I requested. These methods fire events that should be listened to by the Outlook Addin.
private void RegisterConnectionPoint()
{
Logger.Log("RegisterConnectionPoint():");
// Call QueryInterface for IConnectionPointContainer
Foo foo = new Foo();
IConnectionPointContainer icpc = (IConnectionPointContainer)foo;
// Find the connection point for the
// _IFoo source interface
Guid IID_IFoo = typeof(_IFoo).GUID;
icpc.FindConnectionPoint(ref IID_IFoo, out icp);
// Pass a pointer of the host to the connection point
icp.Advise(this, out cookie);
}
My problem is the Outlook Addin never receives the events from the COM object. I think it may be due to the Addin not correctly registering with the COM object, or that there are two COM objects one for the VC++ app and one for the Outlook Addin.
My questions are
Is the basic concept of creating a Outlook VSTO Addin that deletes emails upon receiving an event from a COM server whose events are triggered from a separate process feasible?
If the answer is 'yes' to the first question can anyone see what I am doing wrong?
Debugging the VC++ app side I get to this code which it seems is generated ATL code (I haven't written all the code so am guessing sometimes):
int cConnections = m_vec.GetSize();
for (int iConnection = 0; iConnection < cConnections; iConnection++)
{
pThis->Lock();
CComPtr<IUnknown> punkConnection = m_vec.GetAt(iConnection);
pThis->Unlock();
IDispatch * pConnection = static_cast<IDispatch *>(punkConnection.p);
if (pConnection)
{
CComVariant avarParams[1];
avarParams[0] = attachmentPath;
avarParams[0].vt = VT_BSTR;
CComVariant varResult;
DISPPARAMS params = { avarParams, NULL, 1, 0 };
hr = pConnection->Invoke(1, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD, &params, &varResult, NULL, NULL);
}
}
The problem is m_vec.GetSize() returns 0. So it seems there are no 'connections'. Which would imply I am either creating a different instance of the COM object than the one used by the Outlook Addin or the Addin is not registering correctly.

Answer 1

So the link supplied by #Dmitry was what I needed. By using the Running Object Table (ROT) I was able to get a reference to the Outlook addin loaded by Outlook. So allowing me to call the methods inside it to delete the mail attachment.
Some changes were required including:
Moving registration of the addin to ThisAddin_Startup() as the default OutlookAddin class uses a static constructor so I was not able to reference the Addin inside the constructor.
I also had to move my code to a user session process as this post COMException (0x800401E3): Operation unavailable (Exception from HRESULT: 0x800401E3 (MK_E_UNAVAILABLE)) with scheduled task explains retrieving an COM object from the ROT is not supported for services. This was just a point I thought I should add as it could stump people trying the same thing I was.
Additionally I found the tool ROT viewer found here http://alax.info/blog/1444 useful as you can check if you addin is actually registering to the ROT.
Hope this helps people.