CompareBookmarks, méthode – Exemple (VC++)

S’applique à : Access 2013, Office 2013

Cet exemple illustre le fonctionnement de la méthode CompareBookmarks. La valeur relative des signets est rarement requise sauf si un signet particulier présente une caractéristique spéciale.

Désignez une ligne aléatoire d’un objet Recordset dérivé de la table Authors comme cible d’une recherche. Affichez ensuite la position de chaque ligne par rapport à cette cible.

 
// BeginCompareBookmarksCpp 
#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 <time.h> 
#include <stdlib.h> 
 
// Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void CompareBookMarksX(void); 
void PrintProviderError(_ConnectionPtr pConnection); 
void PrintComError(_com_error &e); 
 
////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
////////////////////////////////////////////////////////// 
 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 CompareBookMarksX(); 
 
 printf("Press any key to continue..."); 
 getch(); 
 ::CoUninitialize(); 
} 
 
////////////////////////////////////////////////////////// 
// // 
// CompareBookMarksX Function // 
// // 
////////////////////////////////////////////////////////// 
 
void CompareBookMarksX(void) 
{ 
 HRESULT hr = S_OK; 
 
 _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';" 
 "Initial Catalog='pubs';Integrated Security='SSPI';"); 
 
 // Initialize pointers on define. 
 // These are in the ADODB:: namespace. 
 _RecordsetPtr pRstAuthors = NULL; 
 _variant_t vTarget; 
 _bstr_t strAns; 
 _bstr_t strTitle; 
 strTitle = "CompareBookmarks Example"; 
 try 
 { 
 TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset))); 
 
 pRstAuthors->Open("SELECT * FROM authors ORDER BY au_id", strCnn, 
 adOpenStatic, adLockReadOnly, adCmdText); 
 
 long count = pRstAuthors->RecordCount; 
 printf("Rows in the Recordset = %d\n", count); 
 if (count == 0) 
 exit(1); //Exit if an empty recordset 
 
 srand( (unsigned)time( NULL ) ); //Randomize 
 
 count = int(rand() % (count-1)); //Get position between 1 and count-1 
 if(!count) {count++;}; 
 
 printf("Randomly chosen row position = %d\n", count); 
 
 _variant_t vtBookMark = (short)adBookmarkFirst; 
 
 pRstAuthors->Move(count,vtBookMark); //Move row to random position 
 
 vTarget = pRstAuthors->Bookmark; //Remember the mystery row. 
 count = 0; 
 long intLineCnt = 3; 
 pRstAuthors->MoveFirst(); 
 
 while (!(pRstAuthors->EndOfFile)) //Loop through recordset 
 { 
 intLineCnt++; 
 if (intLineCnt%20 == 0) 
 { 
 printf("\nPress any key to continue...\n"); 
 getch(); 
 } 
 long result = pRstAuthors->CompareBookmarks( 
 pRstAuthors->Bookmark, vTarget); 
 
 if (result == adCompareNotEqual) 
 printf("Row %d: Bookmarks are not equal. %d\n", count, result); 
 else if (result == adCompareNotComparable) 
 printf("Row %d: Bookmarks are not comparable.\n", count); 
 else 
 { 
 switch(result) 
 { 
 case adCompareLessThan: 
 strAns = "less than"; 
 break; 
 case adCompareEqual: 
 strAns = "equal to"; 
 break; 
 case adCompareGreaterThan: 
 strAns = "greater than"; 
 break; 
 default: 
 strAns = "in error comparing to"; 
 break; 
 } 
 printf ("Row position %d is %s the target.\n", 
 count,(LPCSTR)strAns); 
 } 
 count++; 
 pRstAuthors->MoveNext(); 
 } 
 } 
 catch(_com_error &e) 
 { 
 // Notify the user of errors if any. 
 // Pass a connection pointer accessed from the Recordset. 
 _variant_t vtConnect = pRstAuthors->GetActiveConnection(); 
 
 // GetActiveConnection returns connect string if connection 
 // is not open, else returns Connection object. 
 switch(vtConnect.vt) 
 { 
 case VT_BSTR: 
 PrintComError(e); 
 break; 
 case VT_DISPATCH: 
 PrintProviderError(vtConnect); 
 break; 
 default: 
 printf("Errors occured."); 
 break; 
 } 
 } 
 
 // Clean up objects before exit. 
 if (pRstAuthors) 
 if (pRstAuthors->State == adStateOpen) 
 pRstAuthors->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("Error number: %x\t%s\n", 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); 
} 
// EndCompareBookmarksCpp