DeleteRule Property Example (VC++)

This example demonstrates the DeleteRule property of a Key object. The code appends a new Table and then defines a new primary key, setting DeleteRule to adRICascade.

// BeginDeleteRuleCpp
#import "c:\Program Files\Common Files\system\ado\msadox.dll" \
    no_namespace
#import "c:\Program Files\Common Files\system\ado\msado15.dll"

#include "iostream.h"
#include "stdio.h"
#include "conio.h"

//Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void DeleteRuleX(void);

//////////////////////////////////////////////////////////
//                                                      //
//      Main Function                                   //
//                                                      //
//////////////////////////////////////////////////////////
void main()
{
    if(FAILED(::CoInitialize(NULL)))
        return;

    DeleteRuleX();

    ::CoUninitialize();
}

//////////////////////////////////////////////////////////
//                                                      //
//       DeleteRuleX Function                           //
//                                                      //
//////////////////////////////////////////////////////////
void DeleteRuleX(void)
{
    HRESULT hr = S_OK;

    // Define ADOX object pointers.
    // Initialize pointers on define.
    // These are in the ADOX::  namespace.
    _KeyPtr m_pKeyPrimary = NULL;
    _CatalogPtr m_pCatalog   = NULL;
    _TablePtr m_pTblNew  = NULL;

    // Define string variables.
    _bstr_t strcnn("Provider='Microsoft.JET.OLEDB.4.0';"
                "Data source = 'c:\\Program Files\\Microsoft Office"
                "\\Office\\Samples\\Northwind.mdb';");
    try
    {
        TESTHR(hr = m_pKeyPrimary.CreateInstance(__uuidof(Key)));
        TESTHR(hr = m_pCatalog.CreateInstance(__uuidof (Catalog)));
        TESTHR(hr = m_pTblNew.CreateInstance(__uuidof(Table)));

        // Connect the catalog.
        m_pCatalog->PutActiveConnection(strcnn);

        // Name new table.
        m_pTblNew->Name = "NewTable";

        // Append a numeric and a text field to new table.
        m_pTblNew->Columns->Append("NumField",adInteger,20);
        m_pTblNew->Columns->Append("TextField",adVarWChar,20);

        // Append the new table.
        m_pCatalog->Tables->Append(_variant_t((IDispatch*)m_pTblNew));
        printf("Table 'NewTable' is added.\n");

        // Define the Primary key.
        m_pKeyPrimary->Name = "NumField";
        m_pKeyPrimary->Type = adKeyPrimary;
        m_pKeyPrimary->RelatedTable = "Customers";
        m_pKeyPrimary->Columns->Append("NumField",adInteger,20);
        m_pKeyPrimary->Columns->GetItem("NumField")->RelatedColumn = 
            "CustomerId";
        m_pKeyPrimary->DeleteRule = adRICascade;

        //to pass an optional column parameter to Key's Apppend method
        _variant_t vOptional;
        vOptional.vt = VT_ERROR;
        vOptional.scode = DISP_E_PARAMNOTFOUND;

        // Append the primary key.
        m_pCatalog->Tables->GetItem("NewTable")->Keys->Append(
            _variant_t((IDispatch*)m_pKeyPrimary),
            adKeyPrimary,vOptional,L"",L"");

        // Delete the table as this is a demonstration.
        m_pCatalog->Tables->Delete(m_pTblNew->Name);
        printf("Table 'NewTable' is deleted.\n");
    }

    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 include files...."<< endl;
    }
}
// EndDeleteRuleCpp

See Also

DeleteRule Property | Key Object