GetString, méthode – Exemple (VC++)

S’applique à : Access 2013, Office 2013

Cet exemple illustre la méthode GetString.

Supposons que vous déboguez un problème d'accès aux données et que vous sounaitez un moyen rapide et simple d'imprimer le contenu actuel d'un objet Recordset de petite taille.

 
// BeginGetStringCpp 
#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 <string.h> 
 
// Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void GetStringX(void); 
void PrintProviderError(_ConnectionPtr pConnection); 
void PrintComError(_com_error &e); 
 
////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
////////////////////////////////////////////////////////// 
 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 GetStringX(); 
 
 ::CoUninitialize(); 
} 
 
////////////////////////////////////////////////////////// 
// // 
// GetStringX Function // 
// // 
////////////////////////////////////////////////////////// 
 
void GetStringX(void) 
{ 
 HRESULT hr = S_OK; 
 
 // Define ADO object pointers. 
 // Initialize pointers on define. 
 // These are in the ADODB:: namespace. 
 _ConnectionPtr pConnection = NULL; 
 _RecordsetPtr pRstAuthors = NULL; 
 
 // Define string variables. 
 _bstr_t strCnn("Provider='sqloledb';Data Source='localhost';" 
 "Initial Catalog='Northwind';Integrated Security='SSPI';"); 
 _bstr_t varOutput; 
 char *strPrompt = "Enter a state (CA, IN, KS, MD, MI, OR, TN, UT): "; 
 char strState[2], *pState; 
 
 try 
 { 
 // Open connection. 
 TESTHR(pConnection.CreateInstance(__uuidof(Connection))); 
 
 // Open a command object for a stored procedure, 
 // with one parameter. 
 TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset))); 
 
 printf("%s",strPrompt); 
 gets(strState); 
 
 pState = strtok(strState," \t"); 
 
 char strQry[100] = "SELECT au_fname, au_lname, address, city " 
 "FROM authors WHERE state = "; 
 
 strcat(strQry,"'"); 
 strcat(strQry,pState); 
 strcat(strQry,"'"); 
 
 _bstr_t strQuery(strQry); 
 
 pConnection->Open (strCnn, "", "", adConnectUnspecified); 
 
 pRstAuthors->Open(strQuery, _variant_t((IDispatch*)pConnection, 
 true), 
 adOpenStatic, adLockReadOnly, adCmdText); 
 
 if (pRstAuthors->RecordCount > 0) 
 { 
 // Use all defaults: get all rows, TAB column delimiter, 
 // CARRIAGE RETURN row delimiter, empty-string null delimiter 
 long lRecCount = pRstAuthors->RecordCount; 
 _bstr_t varTab("\t"); 
 _bstr_t varRet("\r"); 
 _bstr_t varNull(""); 
 varOutput = pRstAuthors->GetString(adClipString,lRecCount, 
 varTab,varRet,varNull); 
 printf("State = '%s'\n", strState); 
 printf ("Name Address City\n"); 
 printf ("%s\n", (LPCTSTR)varOutput); 
 } 
 else 
 { 
 printf("\nNo rows found for state = '%s'\n",pState); 
 } 
 // Clean up objects before exit. 
 pRstAuthors->Close(); 
 pConnection->Close(); 
 } 
 
 catch(_com_error &e) 
 { 
 // Notify the user of errors if any. 
 // Pass a connection pointer accessed from the Recordset. 
 PrintProviderError(pConnection); 
 PrintComError(e); 
 } 
} 
 
////////////////////////////////////////////////////////// 
// // 
// 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); 
 
} 
// EndGetStringCpp