Ejemplo de la propiedad DefinedSize (VC++)

Se aplica a: Access 2013, Office 2013

En este ejemplo, se muestra la propiedad DefinedSize de una columna. El código redefinirá el tamaño de la columna Name de la tabla Employees de la base de datos Neptuno. A continuación, se mostrará el cambio en los valores del campo Nombre de un conjunto de registros basándose en la tabla Employees. Tenga en cuenta que, de forma predeterminada, el campo Name se rellenará con espacios cuando haya redefinido la propiedad DefinedSize.

 
// BeginDefinedSizeCpp 
#import "c:\Program Files\Common Files\system\ado\msadox.dll" no_namespace 
#import "C:\Program Files\Common Files\System\ADO\msado15.dll" rename("EOF", "EndOfFile") 
 
#include "iostream.h" 
#include "stdio.h" 
#include "conio.h" 
 
// Function declarations 
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);}; 
void DefinedSizeX(void); 
 
////////////////////////////////////////////////////////// 
// // 
// Main Function // 
// // 
////////////////////////////////////////////////////////// 
void main() 
{ 
 if(FAILED(::CoInitialize(NULL))) 
 return; 
 
 DefinedSizeX(); 
 
 ::CoUninitialize(); 
} 
 
////////////////////////////////////////////////////////// 
// // 
// DefinedSizeX Function // 
// // 
////////////////////////////////////////////////////////// 
void DefinedSizeX(void) 
{ 
 HRESULT hr = S_OK; 
 
 // Define ADOX object pointers. 
 // Initialize pointers on define. 
 // These are in the ADOX:: namespace. 
 _CatalogPtr m_pCatNorthwind = NULL; 
 _ColumnPtr m_pColFirstName = NULL; 
 _ColumnPtr m_pColNewFirstName = NULL; 
 
 // Define ADODB object pointers 
 ADODB::_RecordsetPtr m_pRstEmployees = NULL; 
 
 // Define string variables. 
 _bstr_t strCnn("Provider='Microsoft.JET.OLEDB.4.0';data source=" 
 "'c:\\Program Files\\Microsoft Office\\Office\\Samples\\" 
 "Northwind.mdb';"); 
 _bstr_t aryFirstName[10]; 
 
 try 
 { 
 // Open a Recordset for the Employees table. 
 TESTHR(hr = m_pRstEmployees.CreateInstance( 
 __uuidof(ADODB::Recordset))); 
 TESTHR(hr = m_pCatNorthwind.CreateInstance(__uuidof (Catalog))); 
 TESTHR(hr = m_pColNewFirstName.CreateInstance(__uuidof(Column))); 
 
 m_pRstEmployees->Open("Employees",strCnn,ADODB::adOpenKeyset, 
 ADODB::adLockReadOnly,ADODB::adCmdTable); 
 
 long lngSize = m_pRstEmployees->RecordCount; 
 aryFirstName[lngSize]; 
 
 // Open a catalog for the Northwind database, 
 // using same connection as rstEmployees. 
 m_pCatNorthwind->PutActiveConnection(m_pRstEmployees-> 
 GetActiveConnection()); 
 
 // Loop through the recordset displaying the contents, 
 // of the FirstName field, the field's defined size, 
 // and its actual size. 
 // Also store FirstName values in aryFirstName array. 
 m_pRstEmployees->MoveFirst(); 
 printf("\nOriginal Defined Size and Actual Size"); 
 int iCount=0; 
 while (!(m_pRstEmployees->EndOfFile)) 
 { 
 printf("\nEmployee Name:"); 
 printf("%s ",(LPSTR)(_bstr_t)m_pRstEmployees->Fields-> 
 GetItem("FirstName")->Value); 
 printf("%s\n",(LPSTR)(_bstr_t)m_pRstEmployees->Fields-> 
 GetItem("LastName")->Value); 
 printf(" FirstName Defined size: %d\n",m_pRstEmployees-> 
 Fields->GetItem("FirstName")->DefinedSize) ; 
 printf(" FirstName Actual size: %d\n",m_pRstEmployees-> 
 Fields->GetItem("FirstName")->ActualSize); 
 aryFirstName[iCount] = (_bstr_t) m_pRstEmployees->Fields-> 
 GetItem("FirstName")->Value; 
 m_pRstEmployees->MoveNext(); 
 iCount++; 
 if(iCount%5==0) 
 { 
 printf("Press any key to continue..."); 
 getch(); 
 system("cls"); 
 } 
 } 
 m_pRstEmployees->Close(); 
 
 // Redefine the DefinedSize of FirstName in the catalog. 
 m_pColFirstName = m_pCatNorthwind->Tables->GetItem("Employees")-> 
 Columns->GetItem("FirstName"); 
 m_pColNewFirstName->Name = m_pColFirstName->Name; 
 m_pColNewFirstName->Type = m_pColFirstName->Type; 
 m_pColNewFirstName->DefinedSize = 
 (m_pColFirstName->DefinedSize) + 1; 
 
 // Append new FirstName column to catalog. 
 m_pCatNorthwind->Tables->GetItem("Employees")->Columns-> 
 Delete(m_pColFirstName->Name); 
 m_pCatNorthwind->Tables->GetItem("Employees")->Columns-> 
 Append(_variant_t((IDispatch*)m_pColNewFirstName,true), 
 adVarWChar,m_pColNewFirstName->DefinedSize); 
 
 // Open Employee table in Recordset for updating. 
 m_pRstEmployees->Open("Employees",m_pCatNorthwind-> 
 GetActiveConnection(),ADODB::adOpenKeyset, 
 ADODB::adLockOptimistic,ADODB::adCmdTable); 
 
 // Loop through the recordset displaying the contents 
 // of the FirstName field,the field's defined size, 
 // and its actual size. 
 // Also restore FirstName values from aryFirstName. 
 printf("Press any key to continue..."); 
 getch(); 
 system("cls"); 
 m_pRstEmployees->MoveFirst(); 
 printf("\n\nNew Defined Size and Actual Size"); 
 iCount=0; 
 while (!(m_pRstEmployees->EndOfFile)) 
 { 
 m_pRstEmployees->Fields->GetItem("FirstName")->Value = 
 aryFirstName[iCount]; 
 printf("\nEmployee Name: "); 
 printf("%s ",(LPSTR) (_bstr_t)m_pRstEmployees->Fields-> 
 GetItem("FirstName")->Value); 
 printf("%s\n",(LPSTR)(_bstr_t)m_pRstEmployees->Fields-> 
 GetItem("LastName")->Value); 
 printf(" FirstName Defined size: %d\n",m_pRstEmployees-> 
 Fields->GetItem("FirstName")->DefinedSize ); 
 printf(" FirstName Actual size: %d\n",m_pRstEmployees-> 
 Fields->GetItem("FirstName")->ActualSize ); 
 m_pRstEmployees->MoveNext(); 
 iCount++; 
 if(iCount%5==0) 
 { 
 printf("Press any key to continue..."); 
 getch(); 
 system("cls"); 
 } 
 } 
 m_pRstEmployees->Close(); 
 
 // Restore original FirstName column to catalog 
 m_pCatNorthwind->Tables->GetItem("Employees")->Columns-> 
 Delete(m_pColNewFirstName->Name); 
 
 m_pCatNorthwind->Tables->GetItem("Employees")->Columns-> 
 Append(_variant_t((IDispatch*)m_pColFirstName,true), 
 adVarWChar,m_pColFirstName->DefinedSize); 
 
 // Restore original FirstName values to Employees table. 
 m_pRstEmployees->Open("Employees",m_pCatNorthwind-> 
 GetActiveConnection(),ADODB::adOpenKeyset, 
 ADODB::adLockOptimistic,ADODB::adCmdTable); 
 
 m_pRstEmployees->MoveFirst(); 
 iCount = 0; 
 while(!(m_pRstEmployees->EndOfFile)) 
 { 
 m_pRstEmployees->Fields->GetItem("FirstName")->Value = 
 aryFirstName[iCount]; 
 m_pRstEmployees->MoveNext(); 
 iCount++; 
 } 
 } 
 catch(_com_error &e) 
 { 
 // Notify the user of errors if any. 
 _bstr_t bstrSource(e.Source()); 
 _bstr_t bstrDescription(e.Description()); 
 
 printf("\n\tSource : %s \n\tdescription : %s \n ", 
 (LPCSTR)bstrSource,(LPCSTR)bstrDescription); 
 } 
 catch(...) 
 { 
 cout << "Error occured in DefinedSizeX...."<< endl; 
 } 
 
 if (m_pRstEmployees) 
 if (m_pRstEmployees->State == 1) 
 m_pRstEmployees->Close(); 
 
 m_pCatNorthwind = NULL; 
} 
// EndDefinedSizeCpp