Item, propriété – Exemple (VC++)

S’applique à : Access 2013, Office 2013

Cet exemple montre comment la propriété Item accède aux membres d’une collection. L’exemple ouvre la table Authors de la base de données Pubs avec une commande paramétrable.

Le paramètre de la commande émise sur la base de données est accédé à partir de la collection Parameters de l’objet Command par index et par nom. Les champs de l'objet Recordset retourné sont ensuite accédés à partir de la collection Fields de cet objet par index et par nom.

 
// BeginItemCpp 
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" no_namespace rename("EOF", "EndOfFile") 
 
#include <ole2.h> 
#include <stdio.h> 
#include <conio.h> 
 
// Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void ItemX(void); 
void PrintProviderError(_ConnectionPtr pConnection); 
void PrintComError(_com_error &e); 
 
////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
////////////////////////////////////////////////////////// 
 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 ItemX(); 
 
 //Wait here for the user to see the output 
 printf("Press any key to continue..."); 
 getch(); 
 ::CoUninitialize(); 
} 
 
////////////////////////////////////////////////////////// 
// // 
// ItemX Function // 
// // 
////////////////////////////////////////////////////////// 
 
void ItemX(void) 
{ 
 HRESULT hr = S_OK; 
 
 // Define ADO object pointers. 
 // Initialize pointers on define. 
 // These are in the ADODB:: namespace. 
 _ConnectionPtr pConnection = NULL; 
 _RecordsetPtr pRst = NULL; 
 _CommandPtr pCmd = NULL; 
 _ParameterPtr pPrm = NULL; 
 FieldPtr pFld = NULL; 
 
 // Other Variables. 
 _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';" 
 "Initial Catalog='pubs';Integrated Security='SSPI';"); 
 _variant_t Column[9]; 
 _variant_t vIndex; 
 
 try 
 { 
 // Open connection. 
 TESTHR(pConnection.CreateInstance(__uuidof(Connection))); 
 
 TESTHR(pRst.CreateInstance(__uuidof(Recordset))); 
 
 TESTHR(pCmd.CreateInstance(__uuidof(Command))); 
 
 //Set the array with the authors table field (column) names 
 Column[0] = "au_id"; 
 Column[1] = "au_lname"; 
 Column[2] = "au_fname"; 
 Column[3] = "phone"; 
 Column[4] = "address"; 
 Column[5] = "city"; 
 Column[6] = "state"; 
 Column[7] = "zip"; 
 Column[8] = "contract"; 
 
 _bstr_t strText("SELECT * FROM authors WHERE state = ?"); 
 pCmd->CommandText = strText; 
 
 pPrm = pCmd->CreateParameter("ItemXparm", adChar, adParamInput, 
 2, "CA"); 
 pCmd->Parameters->Append(pPrm); 
 
 pConnection->Open(strCnn, "", "", adConnectUnspecified); 
 pCmd->ActiveConnection = pConnection; 
 
 // Connection and CommandType are omitted because 
 // a Command object is provided. 
 _variant_t Conn; 
 Conn.vt = VT_ERROR; 
 Conn.scode = DISP_E_PARAMNOTFOUND; 
 
 pRst->Open((_variant_t((IDispatch *) pCmd)),Conn,adOpenStatic, 
 adLockReadOnly, -1); 
 
 printf("The Parameters collection accessed by index...\n"); 
 
 vIndex = (short) 0; 
 pPrm = pCmd->Parameters->GetItem(&vIndex); 
 printf("Parameter name = '%s', value = '%s'\n", 
 (LPCSTR)pPrm->Name, (LPSTR)(_bstr_t)pPrm->Value); 
 
 printf("\nThe Parameters collection accessed by name...\n"); 
 pPrm = pCmd->Parameters->Item["ItemXparm"]; 
 printf("Parameter name = '%s', value = '%s'\n", 
 (LPCSTR)pPrm->Name, (LPSTR)(_bstr_t)pPrm->Value); 
 
 printf("\nThe Fields collection accessed by index...\n"); 
 pRst->MoveFirst(); 
 long limit = 0; 
 limit = ((pRst->Fields->Count) - 1); 
 int intLineCnt = 8; 
 for (short iIndex = 0; iIndex <= limit; iIndex++) 
 { 
 vIndex = iIndex; 
 intLineCnt++; 
 if (intLineCnt%15 == 0) 
 { 
 printf("\nPress any key to continue...\n"); 
 getch(); 
 } 
 pFld = pRst->Fields->GetItem(&vIndex); 
 printf("Field %d : Name = '%s', ", iIndex, 
 (LPCSTR)pFld->GetName()); 
 _variant_t FldVal = pFld->GetValue(); 
 
 // Because Value is the default property of a 
 // Property object,the use of the actual keyword 
 // here is optional. 
 switch(FldVal.vt) 
 { 
 case (VT_BOOL): 
 if(FldVal.boolVal) 
 { 
 printf("Value = 'True'"); 
 } 
 else 
 { 
 printf("Value = 'False'"); 
 } 
 printf("\n"); 
 break; 
 case (VT_BSTR): 
 printf("Value = '%s'", 
 (LPCSTR)(_bstr_t)FldVal.bstrVal); 
 printf("\n"); 
 break; 
 case (VT_I4): 
 printf("Value = '%s'",(LPCSTR)FldVal.iVal); 
 printf("\n"); 
 break; 
 case (VT_EMPTY): 
 printf("Value = '%s'",(LPCSTR)FldVal.lVal); 
 printf("\n"); 
 break; 
 default: 
 break; 
 } 
 } 
 
 printf("\nThe Fields collection accessed by name...\n"); 
 pRst->MoveFirst(); 
 for (iIndex = 0; iIndex <= 8; iIndex++) 
 { 
 intLineCnt++; 
 if (intLineCnt%15 == 0) 
 { 
 printf("\nPress any key to continue...\n"); 
 getch(); 
 } 
 pFld = pRst->Fields->GetItem(Column[iIndex]); 
 printf("Field name = '%s', ",(LPCSTR)pFld->GetName()); 
 _variant_t FldVal = pFld->GetValue(); 
 
 // Because Value is the default property of a 
 // Property object,the use of the actual keyword 
 // here is optional. 
 switch(FldVal.vt) 
 { 
 case (VT_BOOL): 
 if(FldVal.boolVal) 
 { 
 printf("Value = 'True'"); 
 } 
 else 
 { 
 printf("Value = 'False'"); 
 } 
 printf("\n"); 
 break; 
 case (VT_BSTR): 
 printf("Value = '%s'", 
 (LPCSTR)(_bstr_t)FldVal.bstrVal); 
 printf("\n"); 
 break; 
 case (VT_I4): 
 printf("Value = '%s'",(LPCSTR)FldVal.iVal); 
 printf("\n"); 
 break; 
 case (VT_EMPTY): 
 printf("Value = '%s'",(LPCSTR)FldVal.lVal); 
 printf("\n"); 
 break; 
 default: 
 break; 
 } 
 } 
 } 
 catch(_com_error &e) 
 { 
 // Notify the user of errors if any. 
 // Pass a connection pointer accessed from the Recordset. 
 PrintProviderError(pConnection); 
 PrintComError(e); 
 } 
 
 // Clean up objects before exit. 
 if (pRst) 
 if (pRst->State == adStateOpen) 
 pRst->Close(); 
 if (pConnection) 
 if (pConnection->State == adStateOpen) 
 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); 
} 
// EndItemCpp