Data Source Object Example

OLE DB Programmer's Reference

The code in this example shows how to create and initialize a data source object.

///////////////////////////////////////////////////////////////// // myCreateDataSource // // This function creates an OLE DB data source object for a // provider selected by the user, sets initialization properties // for the data source, and initializes the data source. The // function returns a pointer to the data source object's // IUnknown in *ppUnkDataSource. // ///////////////////////////////////////////////////////////////// HRESULT myCreateDataSource    (    IUnknown **            ppUnkDataSource    ) {    HRESULT                hr;    IDataInitialize *      pIDataInitialize         = NULL;    IDBPromptInitialize *  pIDBPromptInitialize     = NULL;    IDBInitialize *        pIDBInitialize           = NULL;    CLSID                  clsid                    = CLSID_MSDASQL;    // Use the Microsoft Data Links UI to create the data source    // object; this will allow the user to select the provider    // to connect to and to set the initialization properties    // for the data source object, which will be created by the    // Data Links UI.    if( g_dwFlags & USE_PROMPTDATASOURCE )    {       // Create the Data Links UI object, and obtain the       // IDBPromptInitialize interface from it.       XCHECK_HR(hr = CoCreateInstance(                 CLSID_DataLinks,                   // clsid--Data Links UI                 NULL,                              // pUnkOuter                 CLSCTX_INPROC_SERVER,              // dwClsContext                 IID_IDBPromptInitialize,           // riid                 (void**)&pIDBPromptInitialize));   // ppvObj                       // Invoke the Data Links UI to allow the user to select       // the provider and set initialization properties for       // the data source object that this will create.       XCHECK_HR(hr = pIDBPromptInitialize->PromptDataSource(                 NULL,                             // pUnkOuter                 GetDesktopWindow(),               // hWndParent                 DBPROMPTOPTIONS_PROPERTYSHEET,    // dwPromptOptions                 0,                                // cSourceTypeFilter                 NULL,                             // rgSourceTypeFilter                 NULL,                             // pwszszzProviderFilter                 IID_IDBInitialize,                // riid                 (IUnknown**)&pIDBInitialize));    // ppDataSource                       // We've obtained a data source object from the Data Links UI. This       // object has had its initialization properties set, so all we       // need to do is initialize it.       XCHECK_HR(hr = pIDBInitialize->Initialize());    }    // We are not using the Data Links UI to create the data source    // object. Instead, we will enumerate the providers installed on this    // system through the OLE DB enumerator and will allow the user to    // select the ProgID of the provider for which we will create a    // data source object.    else    {       // Use the OLE DB enumerator to obtain a rowset of installed       // providers, and then allow the user to select a provider from       // this rowset.       CHECK_HR(hr = myCreateEnumerator(CLSID_OLEDB_ENUMERATOR, &clsid));       // We will create the data source object through the OLE DB service       // component IDataInitialize interface, so we need to create an       // instance of the data initialization object.       XCHECK_HR(hr = CoCreateInstance(                 CLSID_MSDAINITIALIZE,         // clsid--data initialize                 NULL,                         // pUnkOuter                 CLSCTX_INPROC_SERVER,         // dwClsContext                 IID_IDataInitialize,          // riid                 (void**)&pIDataInitialize));  // ppvObj                       // Use IDataInitialize::CreateDBInstance to create an uninitialized       // data source object for the chosen provider. By using this       // service component method, the service component manager can       // provide additional functionality beyond what is natively       // supported by the provider if the consumer requests that       // functionality.       XCHECK_HR(hr = pIDataInitialize->CreateDBInstance(                 clsid,                           // clsid--provider                 NULL,                            // pUnkOuter                 CLSCTX_INPROC_SERVER,            // dwClsContext                 NULL,                            // pwszReserved                 IID_IDBInitialize,               // riid                 (IUnknown**)&pIDBInitialize));   // ppDataSource                       // Initialize the data source object by setting any required       // initialization properties and calling IDBInitialize::Initialize.       CHECK_HR(hr = myDoInitialization(pIDBInitialize));    } CLEANUP:    *ppUnkDataSource = pIDBInitialize;    if( pIDataInitialize )       pIDataInitialize->Release();    if( pIDBPromptInitialize )       pIDBPromptInitialize->Release();    return hr; } ///////////////////////////////////////////////////////////////// // myDoInitialization // // This function sets initialization properties that tell the // provider to prompt the user for any information required to // initialize the provider, and then calls the provider's // initialization function. // ///////////////////////////////////////////////////////////////// HRESULT myDoInitialization    (    IUnknown *           pIUnknown    ) {    HRESULT              hr;    IDBInitialize *      pIDBInitialize      = NULL;    IDBProperties *      pIDBProperties      = NULL;    HWND                 hWnd                = GetDesktopWindow();        const ULONG          cProperties         = 2;    DBPROP               rgProperties[cProperties];    DBPROPSET            rgPropSets[1];    // To initialize the data source object, most providers require    // some initialization properties to be set by the consumer. For    // instance, these might include the data source to connect to and the    // user ID and password to use to establish identity. We will ask the    // provider to prompt the user for this required information by    // setting the following properties:    myAddProperty(&rgProperties[0],DBPROP_INIT_PROMPT,VT_I2,                  DBPROMPT_COMPLETE);    myAddProperty(&rgProperties[1],DBPROP_INIT_HWND,  VT_I4,(LONG)hWnd);    rgPropSets[0].rgProperties      = rgProperties;    rgPropSets[0].cProperties      = cProperties;    rgPropSets[0].guidPropertySet   = DBPROPSET_DBINIT;    // Obtain the needed interfaces.    XCHECK_HR(hr = pIUnknown->QueryInterface(IID_IDBProperties,              (void**)&pIDBProperties));    XCHECK_HR(hr = pIUnknown->QueryInterface(IID_IDBInitialize,              (void**)&pIDBInitialize));    // If a provider requires initialization properties, it must support    // the properties that we are setting (_PROMPT and _HWND). However,    // some providers do not need initialization properties and may    // therefore not support the _PROMPT and _HWND properties. Because of    // this, we will not check the return value from SetProperties.    hr = pIDBProperties->SetProperties(1, rgPropSets);    // Now that we've set our properties, initialize the provider.    XCHECK_HR(hr = pIDBInitialize->Initialize()); CLEANUP:    if( pIDBProperties )       pIDBProperties->Release();    if( pIDBInitialize )       pIDBInitialize->Release();    return hr; }

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