Update and CancelUpdate Methods Example (VC++)
This example demonstrates the Update method in conjunction with the CancelUpdate method.
// BeginUpdateCpp
#import "msado15.dll" \
no_namespace rename("EOF", "EndOfFile")
#include <stdio.h>
#include <ole2.h>
#include <malloc.h>
#include <conio.h>
#include "UpdateX.h"
// Function Declartion.
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void UpdateX(void);
void UpdateX2(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
void main()
{
if(FAILED(::CoInitialize(NULL)))
return;
UpdateX();
//Wait here for user to see the output..
printf("\nPress any key to continue...");
getch();
//Clear the screen for the next display
system("cls");
UpdateX2();
::CoUninitialize();
}
//////////////////////////////////////////////////////////
// //
// UpdateX Function //
// //
//////////////////////////////////////////////////////////
void UpdateX(void)
{
HRESULT hr = S_OK;
// 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='MySqlServer';"
"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): ");
char chKey = getch();
if(toupper(chKey) == 'Y')
pRstEmployees->Update();
else
pRstEmployees->CancelUpdate();
//Open an IADORecordBinding interface pointer which
//we'll use 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)
{
// Notify the user of errors if any.
// Pass a 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();
}
// The next example demonstrates the Update method
// in conjunction with the AddNew method.
//////////////////////////////////////////////////////////
// //
// UpdateX2 Function //
// //
//////////////////////////////////////////////////////////
void UpdateX2(void)
{
HRESULT hr = S_OK;
// 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='MySqlServer';"
"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):");
char chKey = getch();
if(toupper(chKey) == 'Y')
{
pRstEmployees->Update();
//Open an IADORecordBinding interface pointer which
//we'll use 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)
{
// Notify the user of errors if any.
// Pass a 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();
}
//////////////////////////////////////////////////////////
// //
// 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,
(LPCSTR) 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);
}
// EndUpdateCpp
UpdateX.h
// BeginUpdateH
#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;
};
// EndUpdateH