Persisted Data Source Objects

SQLOLEDB supports persisted data source objects with the IPersistFile interface.

Examples

A. Persist data source initialization properties

This example shows a function that persists data source initialization properties defining a server, database, and the use of the Windows NT Authentication Mode for connection. The server name and database name are received in the pLocation and pDatasource parameters of the function.

HRESULT SetAndSaveInitProps

    (

    IDBInitialize* pIDBInitialize,

    WCHAR* pDataSource,

    WCHAR* pCatalog,

    BOOL bUseWinNTAuth

    )

    {

    const ULONG     nProps = 4;

    ULONG           nSSProps;

    ULONG           nPropSets;

    ULONG           nProp;

    IDBProperties*  pIDBProperties  = NULL;

    IPersistFile*   pIPersistFile   = NULL;

    DBPROP          aInitProps[nProps];

    DBPROP*         aSSInitProps    = NULL;

    DBPROPSET*      aInitPropSets   = NULL;

    HRESULT         hr;

        nSSProps = 0;

        nPropSets = 1;

    aInitPropSets = new DBPROPSET[nPropSets];

    // Initialize common property options.

    for (nProp = 0; nProp < nProps; nProp++)

        {

        VariantInit(&aInitProps[nProp].vValue);

        aInitProps[nProp].dwOptions = DBPROPOPTIONS_REQUIRED;

        aInitProps[nProp].colid = DB_NULLID;

        }

    // Level of prompting that will be done to complete the connection

    // process.

    aInitProps[0].dwPropertyID = DBPROP_INIT_PROMPT;

    aInitProps[0].vValue.vt = VT_I2;

    aInitProps[0].vValue.iVal = DBPROMPT_NOPROMPT;    

    // Server name.

    aInitProps[1].dwPropertyID = DBPROP_INIT_DATASOURCE;   

    aInitProps[1].vValue.vt = VT_BSTR;

    aInitProps[1].vValue.bstrVal = SysAllocString(pDataSource);

    // Database.

    aInitProps[2].dwPropertyID = DBPROP_INIT_CATALOG;

    aInitProps[2].vValue.vt = VT_BSTR;

    aInitProps[2].vValue.bstrVal = SysAllocString(pCatalog);

    aInitProps[3].dwPropertyID = DBPROP_AUTH_INTEGRATED;

    if (bUseWinNTAuth == TRUE)

    {

        aInitProps[3].vValue.vt = VT_BSTR;

        aInitProps[3].vValue.bstrVal = SysAllocString(L"SSPI");

    } //end if

    // Now that properties are set, construct the PropertySet array.

    aInitPropSets[0].guidPropertySet = DBPROPSET_DBINIT;

    aInitPropSets[0].cProperties = nProps;

    aInitPropSets[0].rgProperties = aInitProps;

    // Set initialization properties

    pIDBInitialize->QueryInterface(IID_IDBProperties,

        (void**) &pIDBProperties);

    hr = pIDBProperties->SetProperties(nPropSets, aInitPropSets);

    if (FAILED(hr))

        {

        // Display error from failed SetProperties.

        }

    pIDBProperties->Release();

    // Free references on OLE known strings.

    for (nProp = 0; nProp < nProps; nProp++)

        {

        if (aInitProps[nProp].vValue.vt == VT_BSTR)

            SysFreeString(aInitProps[nProp].vValue.bstrVal);

        }

    for (nProp = 0; nProp < nSSProps; nProp++)

        {

        if (aSSInitProps[nProp].vValue.vt == VT_BSTR)

            SysFreeString(aInitProps[nProp].vValue.bstrVal);

        }

    // Free dynamically allocated memory.

    delete [] aInitPropSets;

    delete [] aSSInitProps;

    // On success, persist the data source.

    if (SUCCEEDED(hr))

        {

        pIDBInitialize->QueryInterface(IID_IPersistFile,

            (void**) &pIPersistFile);

        hr = pIPersistFile->Save(OLESTR("MyDataSource.txt"), FALSE);

        if (FAILED(hr))

            {

            // Display errors from IPersistFile interface.

            }

        pIPersistFile->Release();

        }

    return (hr);

    }

B. Use persisted data source initialization properties

This example uses a persisted data source object with additional initialization properties that provide a Microsoft® SQL Server™ login ID and password.

HRESULT InitFromPersistedDS

    (

    IDBInitialize* pIDBInitialize,

    WCHAR* pPersistedDSN,

    WCHAR* pUID,

    WCHAR* pPWD

    )

    {

    //const ULONG   nProps = 3;

    const ULONG     nProps = 1;

    const ULONG     nPropSets = 1;

    ULONG           nProp;

    IDBProperties*  pIDBProperties  = NULL;

    IPersistFile*   pIPersistFile   = NULL;

    DBPROP          aInitProps[nProps];

    DBPROPSET       aInitPropSets[nPropSets];

    HRESULT         hr;

    // First load the persisted data source information.

    pIDBInitialize->QueryInterface(IID_IPersistFile,

        (void**) &pIPersistFile);

    hr = pIPersistFile->Load(pPersistedDSN, STGM_DIRECT);

    if (FAILED(hr))

        {

        // Display errors from IPersistFile interface.

        }

    pIPersistFile->Release();

    if (FAILED(hr))

        {

        return (hr);

        }

    // Initialize common property options.

    for (nProp = 0; nProp < nProps; nProp++)

        {

        VariantInit(&aInitProps[nProp].vValue);

        aInitProps[nProp].dwOptions = DBPROPOPTIONS_REQUIRED;

        aInitProps[nProp].colid = DB_NULLID;

        }

    // Level of prompting that will be done to complete the connection

    // process.

    aInitProps[0].dwPropertyID = DBPROP_INIT_PROMPT;

    aInitProps[0].vValue.vt = VT_I2;

    aInitProps[0].vValue.iVal = DBPROMPT_NOPROMPT;     

    // Now that properties are set, construct the PropertySet array.

    aInitPropSets[0].guidPropertySet = DBPROPSET_DBINIT;

    aInitPropSets[0].cProperties = nProps;

    aInitPropSets[0].rgProperties = aInitProps;

    // Set initialization properties

    pIDBInitialize->QueryInterface(IID_IDBProperties,

        (void**) &pIDBProperties);

    hr = pIDBProperties->SetProperties(nPropSets, aInitPropSets);

    if (SUCCEEDED(hr))

        {

        hr = pIDBInitialize->Initialize();

        if (FAILED(hr))

            {

            DumpError(pIDBInitialize, IID_IDBInitialize);

            }

        }

    else

        {

        // Display error from failed SetProperties.

        }

    pIDBProperties->Release();

    // Free references on OLE known strings.

    for (nProp = 0; nProp < nProps; nProp++)

        {

        if (aInitProps[nProp].vValue.vt == VT_BSTR)

            SysFreeString(aInitProps[nProp].vValue.bstrVal);

        }

    return (hr);

    }

The IPersistFile::Save method can be called before or after calling IDBInitialize::Initialize. Calling the method after a successful return from IDBInitialize::Initialize ensures persisting a valid data source specification.