DefinedSize Property Example (VC++)

This example demonstrates the DefinedSize property of a Column. The code will redefine the size of the FirstName column of the Employees table of the Northwind database. Then, the change in the values of the FirstName Field of a Recordset based on the Employees table is displayed. Note that by default, the FirstName field becomes padded with spaces after you redefine the DefinedSize property.

// 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

See Also

Column Object | DefinedSize Property