Seek (méthode) et Index (propriété) – Exemple (VC++)

S’applique à : Access 2013, Office 2013

Cet exemple utilise la méthode Seek et la propriété Index de l’objet Recordset conjointement avec un ID d’employé donné pour localiser le nom de l’employé dans la table Employees de la base de données Nwind.mdb.

 
// BeginSeekCpp 
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" no_namespace rename("EOF", "EndOfFile") 
 
#include <stdio.h> 
#include <ole2.h> 
#include <conio.h> 
#include <string.h> 
#include "SeekX.h" 
 
//Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void SeekX(void); 
void PrintProviderError(_ConnectionPtr pConnection); 
void PrintComError(_com_error &e); 
inline char* mygets(char* strDest, int n) 
{ 
 char strExBuff[10]; 
 char* pstrRet = fgets(strDest, n, stdin); 
 
 if (pstrRet == NULL) 
 return NULL; 
 
 if (!strrchr(strDest, '\n')) 
 // Exhaust the input buffer. 
 do 
 { 
 fgets(strExBuff, sizeof(strExBuff), stdin); 
 }while (!strrchr(strExBuff, '\n')); 
 else 
 // Replace '\n' with '\0' 
 strDest[strrchr(strDest, '\n') - strDest] = '\0'; 
 
 return pstrRet; 
} 
 
////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
////////////////////////////////////////////////////////// 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 SeekX(); 
 
 ::CoUninitialize(); 
} 
 
////////////////////////////////////////////////////////// 
// // 
// SeekX Function // 
// // 
////////////////////////////////////////////////////////// 
void SeekX() 
{ 
 HRESULT hr = S_OK; 
 
 // Define ADO object pointers. 
 // Initialize pointers on define. 
 // These are in the ADODB:: namespace. 
 
 _RecordsetPtr pRstEmp = NULL; 
 
 IADORecordBinding *picRs = NULL; // Interface Pointer declared 
 CEmployeeRs EmpRs; //C++ class object 
 
 //Definitions of other variables 
 _bstr_t strPrompt("Enter an EmployeeID (e.g., 1 to 9)"); 
 char strEmpId[2]; 
 
 try 
 { 
 TESTHR(pRstEmp.CreateInstance(__uuidof(Recordset))); 
 pRstEmp->CursorLocation = adUseServer; 
 pRstEmp->Open("employees", "Provider='Microsoft.Jet.OLEDB.4.0';" 
 "Data Source='C:\\Program Files\\Microsoft Office\\Office\\" 
 "Samples\\Northwind.mdb';", 
 adOpenKeyset,adLockReadOnly,adCmdTableDirect); 
 
 //Open an IADORecordBinding interface pointer which 
 //we'll use for binding Recordset to a Class 
 TESTHR(pRstEmp->QueryInterface( 
 __uuidof(IADORecordBinding), (LPVOID*)&picRs)); 
 
 //Bind the Recordset to a C++ Class 
 TESTHR(picRs->BindToRecordset(&EmpRs)); 
 
 //Does this provider support Seek and Index? 
 if (pRstEmp->Supports(adIndex) && pRstEmp->Supports(adSeek)) 
 { 
 pRstEmp->Index = "PrimaryKey"; 
 
 //Display all the employees. 
 pRstEmp->MoveFirst(); 
 while (!pRstEmp->EndOfFile) 
 { 
 printf("%d : %s %s\n", 
 EmpRs.le_empidStatus == adFldOK ? 
 EmpRs.m_ie_empid : 0, 
 EmpRs.le_fnameStatus == adFldOK ? 
 EmpRs.m_sze_fname : "<NULL>", 
 EmpRs.le_lnameStatus == adFldOK ? 
 EmpRs.m_sze_lname : "<NULL>"); 
 
 pRstEmp->MoveNext(); 
 } 
 //Prompt the user for an EmployeeID between 1 and 9. 
 do 
 { 
 pRstEmp->MoveFirst(); 
 printf("\n\n%s\t",(LPCSTR) strPrompt); 
 mygets(strEmpId, 2); 
 
 //Quit if strEmpID is a zero-length string 
 //(CANCEL, null, etc.) 
 char *strTemp = strtok(strEmpId," \t"); 
 if (strTemp == NULL) break; 
 if (strlen(strTemp) == 1 && atoi(strTemp) >= 1 && 
 atoi(strTemp) <= 9) 
 { 
 _variant_t strEmployeeId(strTemp); 
 pRstEmp->Seek(strEmployeeId, adSeekAfterEQ); 
 if (pRstEmp->EndOfFile) 
 { 
 printf("Employee not found.\n"); 
 } 
 else 
 { 
 printf("%d : Employee='%s %s'\n", 
 EmpRs.le_empidStatus == adFldOK ? 
 EmpRs.m_ie_empid : 0, 
 EmpRs.le_fnameStatus == adFldOK ? 
 EmpRs.m_sze_fname : "<NULL>", 
 EmpRs.le_lnameStatus == adFldOK ? 
 EmpRs.m_sze_lname : "<NULL>"); 
 } 
 } 
 } 
 while(true); 
 } 
 } 
 catch(_com_error &e) 
 { 
 // Notify the user of errors if any. 
 // Pass a connection pointer accessed from the Recordset. 
 _variant_t vtConnect = pRstEmp->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. 
 //Release the IADORecordset Interface here 
 if (picRs) 
 picRs->Release(); 
 
 if (pRstEmp) 
 if (pRstEmp->State == adStateOpen) 
 pRstEmp->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); 
} 
// EndSeekCpp 

SeekX.h

 
// BeginSeekH 
#include "icrsint.h" 
 
// This Class extracts only EmployeeId,FirstName and LastName 
// from employees table 
class CEmployeeRs : public CADORecordBinding 
{ 
BEGIN_ADO_BINDING(CEmployeeRs) 
 
 // Column hiredate is the 1st field in the table. 
 ADO_VARIABLE_LENGTH_ENTRY2(1, adInteger,m_ie_empid, 
 sizeof(m_ie_empid), le_empidStatus, FALSE) 
 
 // Column LastName is the 2nd field in the table. 
 ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_lname, 
 sizeof(m_sze_lname), le_lnameStatus, FALSE) 
 
 // Column FirstName is the 3rd field in the table. 
 ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_fname, 
 sizeof(m_sze_fname), le_fnameStatus, FALSE) 
END_ADO_BINDING() 
 
public: 
 INT m_ie_empid; 
 ULONG le_empidStatus; 
 CHAR m_sze_fname[11]; 
 ULONG le_fnameStatus; 
 CHAR m_sze_lname[21]; 
 ULONG le_lnameStatus; 
}; 
// EndSeekH