Sort Property Example (VC++)

This example uses the Recordset object's Sort property to reorder the rows of a Recordset derived from the Authors table of the Pubs database. A secondary utility routine prints each row.

// BeginSortCpp
#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 SortX(void);
void SortXprint(_bstr_t title, _RecordsetPtr rstp);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

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

    SortX();

    ::CoUninitialize();
}

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

    // 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='MySqlServer';"
            "Initial Catalog='pubs';Integrated Security='SSPI';");

    try
    {
        TESTHR(pConnection.CreateInstance(__uuidof(Connection)));

        TESTHR(pRstAuthors.CreateInstance(__uuidof(Recordset)));

        pRstAuthors->CursorLocation = adUseClient;
        pConnection->Open (strCnn, "", "", adConnectUnspecified);
        pRstAuthors->Open("SELECT * FROM authors",
            _variant_t((IDispatch *) pConnection),
             adOpenStatic, adLockReadOnly, adCmdText);

        SortXprint("    Initial Order    ", pRstAuthors);

        //Clear the screen for the next display.
        printf("\nPress any key to continue...");
        getch();
        system("cls");

        pRstAuthors->Sort = "au_lname ASC, au_fname ASC";
        SortXprint("Last Name Ascending", pRstAuthors);

        //Clear the screen for the next display.
        printf("\nPress any key to continue...");
        getch();
        system("cls");

        pRstAuthors->Sort = "au_lname DESC, au_fname ASC";
        SortXprint("Last Name Descending", pRstAuthors);
    }
    catch(_com_error &e)
    {
        PrintProviderError(pConnection);
        PrintComError(e);
    }

    // Clean up objects before exit.
    if (pRstAuthors)
        if (pRstAuthors->State == adStateOpen)
            pRstAuthors->Close();
    if (pConnection)
        if (pConnection->State == adStateOpen)
            pConnection->Close();
}

//////////////////////////////////////////////////////////
//                                                      //
//        SortXprint Function                           //
//                                                      //
//////////////////////////////////////////////////////////
//This is the secondary utility routine that prints 
//the given title, and the contents of the specified Recordset.
void SortXprint(_bstr_t title, _RecordsetPtr rstp)
{
    printf("---------------%s---------------\n", (LPCSTR)title);
    printf("First Name  Last Name\n"
        "---------------------------------------------------\n");
    rstp->MoveFirst();
    int intLineCnt = 4;
    while (!(rstp->EndOfFile))
    {
        _bstr_t aufname;
        _bstr_t aulname;
        aufname = rstp->GetFields()->GetItem("au_fname")->Value;
        aulname = rstp->GetFields()->GetItem("au_lname")->Value,
        printf("%s    %s\n",(LPCSTR) aufname, (LPCSTR) aulname);
        rstp->MoveNext();
        intLineCnt++;
        if (intLineCnt % 20 ==0)
            {
                printf("\nPress any key to continue...\n");
                getch();    
            }
    }
}

//////////////////////////////////////////////////////////
//                                                      //
//     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, 
                (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);
   
}

// EndSortCpp

See Also

Recordset Object | Sort Property