arcmap - Creating join between feature class and table created with InMemoryWorkspaceFactory?

I'm trying to join a featureclass contained inside a pgdb with a table created with an InMemory Workspace.

The in-memory table contains results that I want to use to define symbology on the featureclass.

The creation of the table goes well, I'm able to see the calculated data, but the IRelationshipClass created returns no records. I tried to use multiple fields to join the data without success. I also added the created table to ArcMap to create the join directcly in ArcMap, without success. It passes all the validations, but returns no records.

I tried to join my inmemory table with a shapefile featureclass instead and it worked.

Here's a sample of code

            // Create an in-memory workspace factory.
            IWorkspaceFactoryPtr ipWorkspaceFactory(CLSID_InMemoryWorkspaceFactory);

            // Create a new in-memory workspace. This returns a name object.
            IWorkspaceNamePtr ipWorkspaceName;
            ipWorkspaceFactory->Create(NULL, L"ValeursCalculees", NULL, 0, &ipWorkspaceName);

            INamePtr ipName(ipWorkspaceName);


            // Open the workspace through the name object.
            IUnknownPtr ipWorkspaceUnk;
            ipName->Open(&ipWorkspaceUnk);
            IWorkspacePtr ipWorkspace(ipWorkspaceUnk);

            IFeatureWorkspacePtr ipMemoryFeatureWorkspace(ipWorkspace);

            IDatasetPtr ipFeatureClassDataset(ipFeatureClass);
            CComBSTR strNomFC;
            ipFeatureClassDataset->get_Name(&strNomFC);


            IFieldsEditPtr ipFieldsEdit(CLSID_Fields);

                      ... Field creation code ...

            ITablePtr ipTable;
            ipMemoryFeatureWorkspace->CreateTable("InMemoryTable", ipFieldsEdit, NULL, NULL, NULL, &ipTable);

                     ... Table Filling code ...


            //IRelQueryTable
            IFeatureWorkspacePtr ipFeatureWorkspace(CTools::GetWorkspaceFromFeatureClass(ipFeatureClass));
            IObjectClassPtr ipObjectClass(ipTable);

            IMemoryRelationshipClassFactoryPtr ipMemoryRelationshipClassFactory(CLSID_MemoryRelationshipClassFactory);
            IRelationshipClassPtr ipRelClass;
            HRESULT hr = ipMemoryRelationshipClassFactory->Open(L"Join", ipFeatureClass, L"Numero_AD", ipObjectClass, L"NumeroAD", L"forward", L"backward", esriRelCardinalityOneToMany, &ipRelClass);

            IDisplayRelationshipClassPtr ipDisplayRelationshipClass(ipFeatureLayer);
            ipDisplayRelationshipClass->DisplayRelationshipClass(ipRelClass, esriLeftOuterJoin);


            //Add the table to ArcMap
            IStandaloneTableCollectionPtr ipStandaloneTableCollection(CTools::GetMap(ipMxDocument));
            IStandaloneTablePtr ipStandaloneTable(CLSID_StandaloneTable);
            ipStandaloneTable->putref_Table(ipTable);
            hr = ipStandaloneTableCollection->AddStandaloneTable(ipStandaloneTable);
            ipMxDocument->UpdateContents();

Am-I trying to do something impossible?

Answer

After experimentation, no, it's not possible to create a valid join between a feature class and a table created with an InMemoryWorkspaceFactory. The join is created but it returns no records. It seems to be a limitation in the interaction between InMemoryWorkspace and Geodatabase workspace.

I found a workaround by replacing the InMemoryWorkspaceFactory with a FileGDBScratchWorkspaceFactory. It's a temporary FileGDB workspace stored in the user's temp folder.

The code looks like this

// Create a scratch (temporary) workspace factory.
IScratchWorkspaceFactory2Ptr ipWorkspaceFactory(CLSID_FileGDBScratchWorkspaceFactory);

// Create a new scratch (temporary) workspace. This returns a name object.
IWorkspaceNamePtr ipWorkspaceName;
IWorkspacePtr ipWorkspace;
ipWorkspaceFactory->CreateNewScratchWorkspace(&ipWorkspace);