MDAC 2.5 SDK - ADO

GetString Method Example (VC++)

See Also

This example demonstrates the GetString method.

Assume you are debugging a data access problem and want a quick, simple way of printing the current contents of a small Recordset.

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

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

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

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

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

    GetStringX();

    ::CoUninitialize();
}

//////////////////////////////////////////////////////////
//                                                      //
//          GetStringX Function                         //
//                                                      //
//////////////////////////////////////////////////////////

void GetStringX(void) 
{
    HRESULT  hr = S_OK;

    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
   _ConnectionPtr  pConnection   = NULL;
   _RecordsetPtr   pRstAuthors   = NULL;

    // Define string variables.
    _bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
            "Initial Catalog=Pubs;User Id=sa;Password=;");
    _bstr_t varOutput; 
    char *strPrompt = "Enter a state (CA, IN, KS, MD, MI, OR, TN, UT): ";
    char strState[2], *pState;

    try
    {
       // Open connection.
        TESTHR(pConnection.CreateInstance(__uuidof(Connection)));

        // Open a command object for a stored procedure, 
        // with one parameter.
        TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));

        printf("%s",strPrompt);
        gets(strState);

        pState = strtok(strState," \t");

        char strQry[100] = "SELECT au_fname, au_lname, address, city "
            "FROM Authors WHERE state = ";

        strcat(strQry,"'");
        strcat(strQry,pState);
        strcat(strQry,"'");

        _bstr_t strQuery(strQry);

        pConnection->Open (strCnn, "", "", NULL);

        pRstAuthors->Open(strQuery, _variant_t((IDispatch*)pConnection,
            true), 
        adOpenStatic, adLockReadOnly, adCmdText);

        if (pRstAuthors->RecordCount > 0) 
        {
            // Use all defaults: get all rows, TAB column delimiter, 
            // CARRIAGE RETURN row delimiter, empty-string null delimiter
            long lRecCount =  pRstAuthors->RecordCount;
            _bstr_t varTab("\t");
            _bstr_t varRet("\r");
            _bstr_t varNull("");
            varOutput = pRstAuthors->GetString(adClipString,lRecCount,
                varTab,varRet,varNull);
            printf("State = '%s'\n", strState);
            printf ("Name            Address                    City\n");
            printf ("%s\n", (LPCTSTR)varOutput);
        }
        else
        {
            printf("\nNo rows found for state = '%s'\n",pState);
        }
        // Clean up objects before exit.
        pRstAuthors->Close();
        pConnection->Close();
   }

   catch(_com_error &e)
   {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
       PrintProviderError(pConnection);
       PrintComError(e);
   }
}

//////////////////////////////////////////////////////////
//                                                      //
//        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("\t Error number: %x\t%s", 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);
   
}