Update and CancelUpdate Methods Example (VC++)

This example demonstrates the Update method in conjunction with the CancelUpdate method.

// Update_CancelUpdate_Methods_Sample.cpp  
// compile with: /EHsc /c  
#import "msado15.dll" no_namespace rename("EOF", "EndOfFile")  

#include <stdio.h>  
#include <ole2.h>  
#include <malloc.h>  
#include <conio.h>  
#include "icrsint.h"  

//This Class extracts only fname,lname from employee table.  
class CEmployeeRs : public CADORecordBinding {  
   BEGIN_ADO_BINDING(CEmployeeRs)  

      // fname is the 1st field in the recordset      
      ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_sze_fname,   
      sizeof(m_sze_fname), le_fnameStatus, FALSE)  

      // lname is the 2nd field in the recordset.  
      ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_lname,   
      sizeof(m_sze_lname), le_lnameStatus, FALSE)     

   END_ADO_BINDING()  

public:  
   CHAR   m_sze_lname[31];  
   ULONG   le_lnameStatus;  
   CHAR   m_sze_fname[21];  
   ULONG   le_fnameStatus;  
};  

// This Class extracts only empid,fname,lname,from employee table.  
class CEmployeeRs1 : public CADORecordBinding {  
   BEGIN_ADO_BINDING(CEmployeeRs1)  

      // emp_id is the 1st field in the table.      
      ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_sze_empid,   
      sizeof(m_sze_empid), le_empidStatus, FALSE)  

      // fname is the 2nd field in the table.  
      ADO_VARIABLE_LENGTH_ENTRY2(2, adVarChar, m_sze_fname,   
      sizeof(m_sze_fname), le_fnameStatus, FALSE)  

      // lname is the 4rt field in the table.  
      ADO_VARIABLE_LENGTH_ENTRY2(4, adVarChar, m_sze_lname,   
      sizeof(m_sze_lname), le_lnameStatus, FALSE)     

   END_ADO_BINDING()  
public:  
   CHAR   m_sze_empid[10];  
   ULONG   le_empidStatus;  
   CHAR   m_sze_lname[31];  
   ULONG   le_lnameStatus;  
   CHAR   m_sze_fname[21];  
   ULONG   le_fnameStatus;     
};  

// Function Declartion.  
inline void TESTHR(HRESULT x) { if FAILED(x) _com_issue_error(x); };  
void UpdateX();  
void UpdateX2();  
void PrintProviderError(_ConnectionPtr pConnection);  
void PrintComError(_com_error &e);  

int main() {  
   if ( FAILED(::CoInitialize(NULL)) )  
      return -1;  

   UpdateX();  
   UpdateX2();  
   ::CoUninitialize();  
}  

void UpdateX() {  
   // Define ADO object pointers.  // Initialize pointers on define.  
   // These are in the ADODB::  namespace.  
   _RecordsetPtr pRstEmployees = NULL;  

   // Define string variables.  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  

   IADORecordBinding *picRs = NULL;   // Interface Pointer declared  
   CEmployeeRs emprs;   // C++ Class object.  

   try {  
      // Open recordset with names from Employee table.  
      TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));  
      pRstEmployees->CursorType = adOpenKeyset;  
      pRstEmployees->LockType = adLockOptimistic;  
      pRstEmployees->Open("SELECT fname, lname FROM Employee "  
         "ORDER BY lname",strCnn,adOpenKeyset,adLockOptimistic, adCmdText);  

      // Store original data.  
      _bstr_t strOldFirst = pRstEmployees->Fields->GetItem("fname")->Value;  
      _bstr_t strOldLast = pRstEmployees->Fields->GetItem("lname")->Value;  

      // Change data in edit buffer.  
      pRstEmployees->Fields->GetItem("fname")->Value = (_bstr_t)("Linda");  
      pRstEmployees->Fields->GetItem("lname")->Value = (_bstr_t)("Kobara");  

      // Show contents of buffer and get user input.  
      printf("\n\nEdit in progress:\n\n");  

      printf("Original data =  %s %s \n", (LPSTR)strOldFirst, (LPSTR)strOldLast);  

      printf("Data in buffer =  %s %s",  
         (LPSTR)(_bstr_t) pRstEmployees->Fields->GetItem("fname")->Value,\  
         (LPSTR) (_bstr_t) pRstEmployees->Fields->GetItem("lname")->Value);  

      // Ask if the User wants to Update  
      printf("\n\nUse Update to replace the original data with the"  
         " buffered data in the Recordset? (y/n): ");  
      int chKey = _getch();  

      if ( toupper(chKey) == 'Y' )  
         pRstEmployees->Update();  
      else   
         pRstEmployees->CancelUpdate();  

      // Open an IADORecordBinding interface pointer for binding Recordset to a class.  
      TESTHR(pRstEmployees->QueryInterface(__uuidof(IADORecordBinding), (LPVOID*)&picRs));  

      // Bind the Recordset to a C++ Class here.  
      TESTHR(picRs->BindToRecordset(&emprs));  

      pRstEmployees->MoveFirst();  

      // Show the resulting data.  
      printf("\nData in recordset =  %s %s", emprs.le_fnameStatus ==   
         adFldOK ? emprs.m_sze_fname : "<NULL>",  
         emprs.le_lnameStatus == adFldOK ?   
         emprs.m_sze_lname : "<NULL>");  

      // Restore original data because this is a demonstration.  
      if ((strcmp((char *)strOldFirst, emprs.m_sze_fname) &&   
         strcmp((char *)strOldLast, emprs.m_sze_lname))) {  
         pRstEmployees->Fields->GetItem("fname")->Value = strOldFirst;  
         pRstEmployees->Fields->GetItem("lname")->Value = strOldLast;  
         pRstEmployees->Update();  
      }   
   }  
   catch(_com_error &e) {      
      // Display errors, if any.  Pass connection pointer accessed from the Recordset.  
      _variant_t vtConnect = pRstEmployees->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 (pRstEmployees)  
      if (pRstEmployees->State == adStateOpen)  
         pRstEmployees->Close();  
}  

void UpdateX2() {  
   // Define ADO object pointers.  Initialize pointers on define.  
   // These are in the ADODB:: namespace.  
   _ConnectionPtr pConnection = NULL;  
   _RecordsetPtr pRstEmployees = NULL;  

   // Define string variables.  
   _bstr_t strCnn("Provider='sqloledb'; Data Source='My_Data_Source'; Initial Catalog='pubs'; Integrated Security='SSPI';");  

   IADORecordBinding *picRs = NULL;   // Interface Pointer declared  
   CEmployeeRs1 emprs;   // C++ Class object.  

   try {  
      // Open a connection.     
      TESTHR(pConnection.CreateInstance(__uuidof(Connection)));  
      pConnection->Open(strCnn, "", "", NULL);  

      // Open recordset with data from Employee table.  
      TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));  
      pRstEmployees->CursorType = adOpenKeyset;  
      pRstEmployees->LockType = adLockOptimistic;  
      pRstEmployees->Open("employee", _variant_t((IDispatch*)pConnection,true),  
         adOpenKeyset, adLockOptimistic, adCmdTable);  

      pRstEmployees->AddNew();  
      _bstr_t strEmpID = "B-S55555M";  
      pRstEmployees->Fields->GetItem("emp_id")->Value = strEmpID;  
      pRstEmployees->Fields->GetItem("fname")->Value = (_bstr_t) ("Bill");  
      pRstEmployees->Fields->GetItem("lname")->Value = (_bstr_t) ("Sornsin");  

      // Show contents of buffer and get user input.  
      printf("\n\nAddNew in progress:\n\n");  

      printf("Data in buffer = %s ,  %s %s",  
         (LPSTR) (_bstr_t) pRstEmployees->Fields->GetItem("emp_id")->Value,  
         (LPSTR) (_bstr_t) pRstEmployees->Fields->GetItem("fname")->Value,  
         (LPSTR) (_bstr_t) pRstEmployees->Fields->GetItem("lname")->Value);  

      printf("\n\nUse Update to save buffer to recordset?(y/n):");  
      int chKey = _getch();  

      if ( toupper(chKey) == 'Y') {  
         pRstEmployees->Update();  

         // Open IADORecordBinding interface pointer for binding Recordset to a class.  
         TESTHR(pRstEmployees->QueryInterface(__uuidof(IADORecordBinding),(LPVOID*)&picRs));  

         // Bind the Recordset to a C++ Class here      
         TESTHR(picRs->BindToRecordset(&emprs));  

         // Go to the new record and show the resulting data.  
         printf ("\n\nData in recordset =  %s ,  %s %s",  
            emprs.le_empidStatus == adFldOK ?   
            emprs.m_sze_empid : "<NULL>",  
            emprs.le_fnameStatus == adFldOK ?   
            emprs.m_sze_fname : "<NULL>",  
            emprs.le_lnameStatus == adFldOK ?   
            emprs.m_sze_lname : "<NULL>");  
      }  
      else {  
         pRstEmployees->CancelUpdate();  
         printf("\n\nNo new record added.\n");  
      }  
      // Delete new data because this is a demonstration.  
      _bstr_t strSQLDelete("DELETE FROM employee WHERE emp_id = '" + strEmpID + "'");  
      pConnection->Execute(strSQLDelete, NULL, adExecuteNoRecords);  
   }  

   catch(_com_error &e) {  
      // Display errors, if any. Pass connection pointer accessed from the Connection.  
      PrintProviderError(pConnection);  
      PrintComError(e);  
   }  

   // Clean up objects before exit.  Release the IADORecordset Interface here     
   if (picRs)  
      picRs->Release();  

   if (pRstEmployees)  
      if (pRstEmployees->State == adStateOpen)  
         pRstEmployees->Close();  
   if (pConnection)  
      if (pConnection->State == adStateOpen)  
         pConnection->Close();  
}  

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);  
}  

See Also

CancelUpdate Method (ADO)
Update Method