Sort, exemple de propriétés (VC++)

Cet exemple utilise la propriété Sort de l’objet Recordset pour réorganiser les lignes d’un Recordset dérivé de la table Authors de la base de données Pubs. Une routine utilitaire secondaire imprime chaque ligne.

// SortPropertyExample.cpp  
// compile with: /EHsc  
#import "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 SortX();  
void SortXprint(_bstr_t title, _RecordsetPtr rstp);  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  
  
int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1;  
   SortX();  
   ::CoUninitialize();  
}  
  
void SortX() {  
   // 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='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  
  
   try {  
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
      TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));  
  
      pRstAuthors->CursorLocation = adUseClient;  
      pConnection->Open (strCnn, "", "", adConnectUnspecified);  
      pRstAuthors->Open("SELECT * FROM authors",  
         _variant_t((IDispatch *) pConnection),  
         adOpenStatic, adLockReadOnly, adCmdText);  
  
      SortXprint("    Initial Order    ", pRstAuthors);  
  
      pRstAuthors->Sort = "au_lname ASC, au_fname ASC";  
      SortXprint("Last Name Ascending", pRstAuthors);  
  
      pRstAuthors->Sort = "au_lname DESC, au_fname ASC";  
      SortXprint("Last Name Descending", pRstAuthors);  
   }  
   catch(_com_error &e) {  
      PrintProviderError(pConnection);  
      PrintComError(e);  
   }  
  
   // Clean up objects before exit.  
   if (pRstAuthors)  
      if (pRstAuthors->State == adStateOpen)  
         pRstAuthors->Close();  
   if (pConnection)  
      if (pConnection->State == adStateOpen)  
         pConnection->Close();  
}  
  
// This is the secondary utility routine that prints   
// the given title, and the contents of the specified Recordset.  
void SortXprint(_bstr_t title, _RecordsetPtr rstp) {  
   printf("---------------%s---------------\n", (LPCSTR)title);  
   printf("First Name  Last Name\n"  
      "---------------------------------------------------\n");  
   rstp->MoveFirst();  
   while (!(rstp->EndOfFile)) {  
      _bstr_t aufname;  
      _bstr_t aulname;  
      aufname = rstp->GetFields()->GetItem("au_fname")->Value;  
      aulname = rstp->GetFields()->GetItem("au_lname")->Value,  
         printf("%s    %s\n",(LPCSTR) aufname, (LPCSTR) aulname);  
      rstp->MoveNext();  
   }  
}  
  
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, (LPCSTR) pErr->Description);  
      }  
   }  
}  
  
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);  
}  

Voir aussi

Recordset, objet (ADO)
Sort, propriété