State Property Example (VC++)

This example uses the State property to display a message while asynchronous connections are opening and asynchronous commands are executing.

// BeginStateCpp
#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 StateX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);

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

    StateX();

    ::CoUninitialize();
}

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

    // Define string variables.
    _bstr_t strSQLChange("UPDATE Titles SET Type = "
            "'self_help' WHERE Type = 'psychology'");
    _bstr_t strSQLRestore("UPDATE Titles SET Type = "
            "'psychology' WHERE Type = 'self_help'");
    _bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';"
            "Initial Catalog='pubs';Integrated Security='SSPI';");

    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _ConnectionPtr    pConnection        = NULL;
    _ConnectionPtr    pConnection2        = NULL;
    _CommandPtr         pCmdChange    = NULL;
    _CommandPtr         pCmdRestore    = NULL;

    try
    {
        // Open two asynchronous connections,displaying
        // a message while connecting.
        TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
        TESTHR(pConnection2.CreateInstance(__uuidof(Connection)));

        pConnection->Open (strCnn, "", "", adAsyncConnect);
        while(pConnection->State == adStateConnecting)
        {
            printf("Opening first connection....\n\n");
        }

        pConnection2->Open (strCnn, "", "", adAsyncConnect);
        while(pConnection2->State == adStateConnecting)
        {
            printf("Opening second connection....\n\n");
        }

        // Create two command objects.
        TESTHR(pCmdChange.CreateInstance(__uuidof(Command)));
        pCmdChange->ActiveConnection = pConnection;
        pCmdChange->CommandText = strSQLChange;

        TESTHR(pCmdRestore.CreateInstance(__uuidof(Command)));
        pCmdRestore->ActiveConnection = pConnection2;
        pCmdRestore->CommandText = strSQLRestore;

        // Executing the commands,displaying a message 
        // while they are executing.
        pCmdChange->Execute(NULL,NULL,adAsyncExecute);
        while(pCmdChange->State == adStateExecuting)
        {
            printf("Change command executing...\n\n");
        }

        pCmdRestore->Execute(NULL,NULL,adAsyncExecute);
        while(pCmdRestore->State == adStateExecuting)
        {
            printf("Restore command executing...\n\n");
        }
    }
    catch (_com_error &e)
    {
        // Notify the user of errors if any.
        PrintProviderError(pConnection);
        PrintComError(e);
    }

    if (pConnection)
        if (pConnection->State == adStateOpen)
            pConnection->Close();
    if (pConnection2)
        if (pConnection2->State == adStateOpen)
            pConnection2->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, 
                (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);
}
// EndStateCpp

See Also

State Property