Microsoft OLE DB 2.0 Programmers Reference and Data Access SDK (Microsoft Professional Editions)

2017-07-07 02:10:07

OLE DB Programmer's Reference

Initializes a data source object or enumerator.

HRESULT Initialize();

Parameters

None.

Return Code

S_OK

The method succeeded.

DB_S_ASYNCHRONOUS

The method has initiated asynchronous initialization of the data source object. The consumer can call IDBAsynchStatus::GetStatus to poll for status or can register for notifications of asynchronous processing. Until asynchronous processing completes, the data source object remains in an uninitialized state.

DB_S_ASYNCHRONOUS should be returned before DB_S_ERRORSOCCURRED.

DB_S_ERRORSOCCURRED

The data source object or enumerator was initialized, but one or more properties—for which the dwOptions element of the DBPROP structure was DBPROPOPTIONS_OPTIONAL—were not set. To return properties in error, the provider uses DBPROPSET_PROPERTIESINERROR as described in Chapter 14: Properties. The method can fail to set properties for a number of reasons, including the following:

It was not possible to set the property.

The value in vValue in the DBPROP structure was invalid.

The property's value conflicted with an existing property.

DB_S_ASYNCHRONOUS should be returned before DB_S_ERRORSOCCURRED. Once rowset population is complete, the consumer can see DB_S_ERRORSOCCURRED either by calling IDBAsynchStatus::GetStatus or by receiving IDBAsynchNotify::OnStop.

E_FAIL

A provider-specific error occurred.

E_OUTOFMEMORY

The provider was unable to allocate sufficient memory to initialize the data source object or enumerator.

E_UNEXPECTED

The data source object is in the process of being initialized asynchronously. To cancel asynchronous execution, call IDBAsynchStatus::Abort.

DB_E_ALREADYINITIALIZED

IDBInitialize::Initialize had already been called for the data source object or enumerator, and an intervening call to IDBInitialize::Uninitialize had not been made.

DB_E_CANCELED

The provider prompted for additional information and the user selected Cancel.

DB_E_ERRORSOCCURRED

It was not possible to set the property.

The value in vValue in the DBPROP structure was invalid.

The property's value conflicted with an existing property.

DB_SEC_E_AUTH_FAILED

Authentication of the consumer to the data source object or enumerator failed. The data source object or enumerator remains in the uninitialized state.

Comments

IDBInitialize::Initialize initializes the data source object or enumerator. It uses the values of properties in the Initialization property group that have been set with IDBProperties::SetProperties. If the consumer has not set values for all required properties, IDBInitialize::Initialize can prompt for values.

If IDBInitialize::Initialize returns DB_S_ERRORSOCCURRED or DB_E_ERRORSOCCURRED, the consumer can immediately call IDBProperties::GetProperties with the DBPPROPSET_PROPERTIESINERROR property set to return the properties that could not be set. For more information, see "Property Sets" in Appendix C: OLE DB Properties.

For information about what the consumer can and cannot do with a data source object or enumerator before it is initialized, see "Data Source Object States" and "Enumerator States" in Chapter 2: Data Source and Session Objects.

Initializing a Data Source Object Through a Network Connection

The following shows how to instantiate a data source object as an in-process object using CoCreateInstance.

#include <oledb.h> extern CLSID CLSID_DSO; int main() { HRESULT hr; IDBInitialize * pIDBInitialize; // Create the data source object. hr = CoCreateInstance(CLSID_DSO, NULL, CLSCTX_INPROC_SERVER, IID_IDBInitialize, (void**) &pIDBInitialize); // Set the initialization properties. DBPROP rgProps[8]; for (ULONG i = 0; i <= 7; i++) { VariantInit(&rgProps[i].vValue); rgProps[i].dwOptions = DBPROPOPTIONS_REQUIRED; }; rgProps[0].dwPropertyID = DBPROP_INIT_LOCATION; V_VT(&(rgProps[0].vValue)) = VT_BSTR; V_BSTR(&(rgProps[0].vValue)) = SysAllocStringLen(OLESTR("server"), wcslen(OLESTR("server"))); rgProps[1].dwPropertyID = DBPROP_INIT_DATASOURCE; V_VT(&(rgProps[1].vValue)) = VT_BSTR; V_BSTR(&(rgProps[1].vValue)) = SysAllocStringLen(OLESTR("database"), wcslen(OLESTR("database"))); rgProps[2].dwPropertyID = DBPROP_AUTH_PASSWORD; V_VT(&(rgProps[2].vValue)) = VT_BSTR; V_BSTR(rgProps[2].vValue) = SysAllocStringLen(OLESTR("password"), wcslen(OLESTR("password"))); rgProps[3].dwPropertyID = DBPROP_AUTH_USERID; V_VT(&(rgProps[3].vValue)) = VT_BSTR; V_BSTR(&(rgProps[3].vValue)) = SysAllocStringLen(OLESTR("username"), wcslen(OLESTR("username"))); rgProps[4].dwPropertyID = DBPROP_AUTH_ENCRYPT_PASSWORD; V_VT(&(rgProps[4].vValue)) = VT_BOOL; V_BOOL(&(rgProps[4].vValue)) = VARIANT_TRUE; rgProps[5].dwPropertyID = DBPROP_AUTH_CACHE_AUTHINFO; V_VT(&(rgProps[5].vValue)) = VT_BOOL; V_BOOL(&(rgProps[5].vValue)) = VARIANT_TRUE; rgProps[6].dwPropertyID = DBPROP_AUTH_PERSIST_SENSITIVE_AUTHINFO; V_VT(&(rgProps[6].vValue)) = VT_BOOL; V_BOOL(&(rgProps[6].vValue)) = VARIANT_TRUE; rgProps[7].dwPropertyID = DBPROP_AUTH_PERSIST_ENCRYPTED; V_VT(&(rgProps[7].vValue)) = VT_BOOL; V_BOOL(&(rgProps[7].vValue)) = VARIANT_TRUE; // Create the structure containing the properties. DBPROPSET PropSet; PropSet.rgProperties = rgProps; PropSet.cProperties = 8; PropSet.guidPropertySet = DBPROPSET_DBINIT; // Get an IDBProperties pointer and set the // initialization properties. IDBProperties *pIDBProperties; pIDBInitialize->QueryInterface(IID_IDBProperties, (void**)&pIDBProperties); pIDBProperties->SetProperties(1, &PropSet); pIDBProperties->Release(); // Initialize the data source object. hr = pIDBInitialize->Initialize(); pIDBInitialize->Release(); return hr; };

Initializing a Data Source Object Through a Network Connection

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