Value Property Example (VC++)

Value Property Example (VC++)

This example demonstrates the Value property with Field and Property objects by displaying field and property values for the Employees table.

#import "c:\Program Files\Common Files\System\ADO\msado15.dll" \
    no_namespace rename("EOF", "EndOfFile")

#include <ole2.h>
#include <stdio.h>
#include <conio.h>

// Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void ValueX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

//////////////////////////////////////////////////////////
//                                                      //
//    Main Function                                     //
//                                                      //
//////////////////////////////////////////////////////////

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

    ValueX();

    ::CoUninitialize();
}

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

    // Define string variables.
   _bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
            "Initial Catalog=Pubs;User Id=sa;Password=;");

    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _RecordsetPtr  pRstEmployees  = NULL;
    FieldsPtr    pFldLoop    = NULL;
    PropertiesPtr  pPrpLoop    = NULL;
    _variant_t vtIndex;
    vtIndex.vt = VT_I2;

       try
    {
        // Open recordset with data from Employees table.
        TESTHR(pRstEmployees.CreateInstance(__uuidof(Recordset)));
        pRstEmployees->Open ("Employees",strCnn ,
            adOpenForwardOnly, adLockReadOnly, adCmdTable);

        printf("Field values in rstEmployees\n\n");

        // Enumerate the Fields collection of the Employees table.
        pFldLoop = pRstEmployees->GetFields();  

        for (int intFields = 0; intFields < (int)pFldLoop->
    GetCount(); intFields++)
        {
            vtIndex.iVal = intFields;

            // Because Value is the default property of a 
            // Field object,the use of the actual keyword 
            // here is optional.
            printf(" %s = %s\n\n" ,
                (LPCSTR) pFldLoop->GetItem(vtIndex)->GetName(),
                (LPCSTR) (_bstr_t) pFldLoop->GetItem(vtIndex)->Value);
        }

        printf("Press any key to continue...\n\n");
        getch();
        printf("Property values in rstEmployees\n\n");

        // Enumerate the Properties collection of the Recordset object.
        pPrpLoop = pRstEmployees->GetProperties();
        int intLine = 0;

        for (int intProperties = 0; intProperties < (int)pPrpLoop->
            GetCount(); intProperties++)
        {
            vtIndex.iVal = intProperties;

            // Because Value is the default property of a
            // Property object,the use of the actual keyword
            // here is optional.
            _variant_t propValue = pPrpLoop->GetItem(vtIndex)->Value;
            switch(propValue.vt)
            {

            case (VT_BOOL):
                     if(propValue.boolVal)
                     {
                        printf(" %s = True\n\n",(LPCSTR) pPrpLoop->
                            GetItem(vtIndex)->GetName());
                     }
                     else
                     {
                         printf(" %s = False\n\n",(LPCSTR) pPrpLoop->
                            GetItem(vtIndex)->GetName());
                     }
                break;

            case (VT_I4):
                printf(" %s = %d\n\n",(LPCSTR) pPrpLoop->
                    GetItem(vtIndex)->GetName(),
                    pPrpLoop->GetItem(vtIndex)->Value.lVal);
                break;

            case (VT_EMPTY):
                printf(" %s = \n\n",(LPCSTR) pPrpLoop->
                    GetItem(vtIndex)->GetName());
                break;

            default:
                break;
            }

            intLine++;
                if (intLine % 10 == 0)
                {
                    printf("\nPress any key to continue...");
                     getch();

                    //Clear the screen for the next display   
                    system("cls"); 
                }
        }

        pRstEmployees->Close();
    }

    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;
        }
    }
}

//////////////////////////////////////////////////////////
//                                                      //
//    PrintProviderError Function                       //
//                                                      //
//////////////////////////////////////////////////////////
void PrintProviderError(_ConnectionPtr pConnection)
{
    // Print Provider Errors from Connection object.
    // pErr is a record object in the Connection’s Errors 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);
}