This example demonstrates the OriginalValue and UnderlyingValue properties by displaying a message if a record's underlying data has changed during a Recordset batch update.
// BeginOriginalValueCpp #import "c:\Program Files\Common Files\System\ADO\msado15.dll" \ no_namespace rename("EOF", "EndOfFile") #include <ole2.h> #include <stdio.h> #include <conio.h> #include "OriginalValueX.h" // Function declarations inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; void OriginalValueX(void); void PrintProviderError(_ConnectionPtr pConnection); void PrintComError(_com_error &e); /////////////////////////////////////////////////////////// // // // Main Function // // // /////////////////////////////////////////////////////////// void main() { if(FAILED(::CoInitialize(NULL))) return; OriginalValueX(); ::CoUninitialize(); } /////////////////////////////////////////////////////////// // // // OriginalValueX Function // // // /////////////////////////////////////////////////////////// void OriginalValueX(void) { // Define ADO object pointers. // Initialize pointers on define. // These are in the ADODB:: namespace. _ConnectionPtr pConnection = NULL; FieldPtr pFldType = NULL; _RecordsetPtr pRstTitles = NULL; // Define string variables. _bstr_t strSQLChange("UPDATE Titles SET Type = " "'sociology' WHERE Type = 'psychology'"); _bstr_t strSQLRestore("UPDATE Titles SET Type = " "'psychology' WHERE Type = 'sociology'"); // Define Other Variables HRESULT hr = S_OK; IADORecordBinding *picRs = NULL; //Interface Pointer declared CTitleRs titlers; // C++ Class object try { _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';" "Initial Catalog='pubs';Integrated Security='SSPI';"); // Open connection. TESTHR(pConnection.CreateInstance(__uuidof(Connection))); pConnection->Open (strCnn, "", "", adConnectUnspecified); // Open Recordset for batch update. TESTHR(pRstTitles.CreateInstance(__uuidof(Recordset))); pRstTitles->PutActiveConnection( _variant_t((IDispatch *)pConnection,true)); pRstTitles->CursorType = adOpenKeyset; pRstTitles->LockType = adLockBatchOptimistic; // Cast Connection pointer to an IDispatch type so converted // to correct type of variant. pRstTitles->Open("Titles", _variant_t((IDispatch *)pConnection,true), adOpenKeyset, adLockBatchOptimistic, adCmdTable); //Open an IADORecordBinding interface pointer which //we'll use for Binding Recordset to a class. TESTHR(pRstTitles->QueryInterface( __uuidof(IADORecordBinding),(LPVOID*)&picRs)); //Bind the Recordset to a C++ Class here TESTHR(picRs->BindToRecordset(&titlers)); // Set field object variable for Type field. pFldType = pRstTitles->Fields->GetItem("type"); // Change the type of psychology titles. while(!(pRstTitles->EndOfFile)) { if (!strcmp(strtok((char *)titlers.m_szau_Type," "), "psychology")) { pFldType->Value = "self_help"; } pRstTitles->MoveNext(); } // Simulate a change by another user by updating data // using a command string. pConnection->Execute(strSQLChange,NULL,0); // Check for changes. pRstTitles->MoveFirst(); while(!(pRstTitles->EndOfFile)) { if (strcmp(pFldType->OriginalValue.pcVal, pFldType->UnderlyingValue.pcVal)) { printf("\n\nData has changed!"); printf("\n\nTitle ID: %s",titlers.lau_Title_idStatus == adFldOK ? titlers.m_szau_Title_id : "<NULL>"); printf("\n\nCurrent Value: %s", (LPCSTR) (_bstr_t) pFldType->Value); printf("\n\nOriginal Value: %s", (LPCSTR) (_bstr_t) pFldType->OriginalValue); printf("\n\nUnderlying Value: %s\n\n", (LPCSTR) (_bstr_t) pFldType->UnderlyingValue); printf("Press any key to continue..."); getch(); system("cls"); } pRstTitles->MoveNext(); } } catch (_com_error &e) { // Notify the user of errors if any. // Pass a connection pointer accessed from the Connection. PrintProviderError(pConnection); PrintComError(e); } // Clean up objects before exit. //Release the IADORecordset Interface here if (picRs) picRs->Release(); if (pRstTitles) if (pRstTitles->State == adStateOpen) { // Cancel the update because this is a demonstration. pRstTitles->CancelBatch(adAffectAll); pRstTitles->Close(); } if (pConnection) if (pConnection->State == adStateOpen) { // Restore Original Values. pConnection->Execute(strSQLRestore,NULL,0); pConnection->Close(); } }; /////////////////////////////////////////////////////////// // // // PrintProviderError Function // // // /////////////////////////////////////////////////////////// void PrintProviderError(_ConnectionPtr pConnection) { // Print Provider Errors from Connection object. // pErr is a record object in the Connection's Error collection. ErrorPtr pErr = NULL; if( (pConnection->Errors->Count) > 0) { long nCount = pConnection->Errors->Count; // Collection ranges from 0 to nCount -1. for(long i = 0;i < nCount;i++) { pErr = pConnection->Errors->GetItem(i); printf("\t Error number: %x\t%s", pErr->Number, pErr->Description); } } } /////////////////////////////////////////////////////////// // // // PrintComError Function // // // /////////////////////////////////////////////////////////// void PrintComError(_com_error &e) { _bstr_t bstrSource(e.Source()); _bstr_t bstrDescription(e.Description()); // Print COM errors. printf("Error\n"); printf("\tCode = %08lx\n", e.Error()); printf("\tCode meaning = %s\n", e.ErrorMessage()); printf("\tSource = %s\n", (LPCSTR) bstrSource); printf("\tDescription = %s\n", (LPCSTR) bstrDescription); } // EndOriginalValueCpp
OriginalValueX.h
// BeginOriginalValueH #include "icrsint.h" //This class extracts title_id and type from titles table class CTitleRs : public CADORecordBinding { BEGIN_ADO_BINDING(CTitleRs) // Column title_id is the 1st field in the Recordset ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_szau_Title_id, sizeof(m_szau_Title_id), lau_Title_idStatus, FALSE) // Column type is the 3rd field in the Recordset ADO_VARIABLE_LENGTH_ENTRY2(3, adVarChar, m_szau_Type, sizeof(m_szau_Type), lau_TypeStatus, TRUE) END_ADO_BINDING() public: CHAR m_szau_Title_id[7]; ULONG lau_Title_idStatus; CHAR m_szau_Type[13]; ULONG lau_TypeStatus; }; // EndOriginalValueH
OriginalValue Property | Recordset Object | UnderlyingValue Property