Count Property Example (VC++)

This example demonstrates the Count property with two collections in the Employee database. The property obtains the number of objects in each collection, and sets the upper limit for loops that enumerate these collections. Another way to enumerate these collections without using the Count property would be to use For Each...Next statements.

// BeginCountCpp
#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 CountX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

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

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

    CountX();

    //Wait here for user to see the output..
    printf("\nPress any key to Exit...");
    getch();

    ::CoUninitialize();
}

///////////////////////////////////////////////////////////
//                                                       //
//      CountX Function                                  //
//                                                       //
///////////////////////////////////////////////////////////

void CountX()
{
    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace
    _RecordsetPtr pRstEmployee = NULL;

    //Define Other Variables
    HRESULT hr = S_OK;
    _variant_t Index;
    Index.vt = VT_I2;
    int j = 0;

    _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';"
        "Initial Catalog='pubs';Integrated Security='SSPI';");

    try
    {
        // Open recordset with data from Employee table.
        TESTHR(pRstEmployee.CreateInstance(__uuidof(Recordset)));
        pRstEmployee->Open("Employee", strCnn, adOpenForwardOnly,
            adLockReadOnly, adCmdTable);
    
        // Print information about Fields collection.
        printf("%d Fields in Employee\n", pRstEmployee->Fields->Count);
        for (int intLoop = 0;
             intLoop <= (pRstEmployee->Fields->Count-1);
             intLoop++)
        {
            Index.iVal = intLoop;
            printf(" %s\n",(LPSTR) pRstEmployee->Fields->
                GetItem(Index)->Name);
        }

        // Print information about Properties collection.
        printf("\n%d Properties in Employee\n", pRstEmployee->
            Properties->Count);
        for (intLoop = 0; 
             intLoop <= (pRstEmployee->Properties->Count - 1);
             intLoop++)
        {
            j++;
            Index.iVal = intLoop;
            printf(" %s\n" ,(LPSTR)pRstEmployee->Properties->
                GetItem(Index)->Name);
            if (((j % 23) == 0) || (intLoop == 11))
            {
                printf("\nPress any key to continue...");
                getch();

                //Clear the screen for the next display   
                system("cls"); 
                j = 0;
            }
        }
    }
    catch(_com_error &e)
    {
        // Notify user of any errors that result from
        // executing the query.
        // Pass a connection pointer accessed from the Recordset.
        _variant_t vtConnect = pRstEmployee->GetActiveConnection();
            
        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.
    if (pRstEmployee)
        if (pRstEmployee->State == adStateOpen)
            pRstEmployee->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,
                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);
}
// EndCountCpp

See Also

Count Property