請教有關atl客戶端應用的問題

Question

是不是第一種方法還缺點什麽，爲什麽我在調試是一到p->dosomething() 就報錯。

Answer 1

第一种方法
用了智能指针
就是说，你不用去管应用计数了
还有，你有没有忘了CoInitialize?

Answer 2

另外，p要首先CreateInstance的说

Answer 3

Copy一段啊ado的例子
 ADO 2.7 Samples  See Also
Resync Method© 1998-2001 Microsoft Corporation. All rights reserved.
Resync Method Example (VC++)
This example demonstrates using the Resync method to refresh data in a static recordset.// BeginResyncCpp
#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 ResyncX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);/////////////////////////////
//                         //
//    Main Function        //
//                         //
/////////////////////////////void main()
{
    if(FAILED(::CoInitialize(NULL)))
        return;    ResyncX();    ::CoUninitialize();
}/////////////////////////////////
//                             //
//     ResyncX Function        //
//                             //
/////////////////////////////////void ResyncX(void) 
{
    HRESULT  hr = S_OK;    // Define string variables.
    _bstr_t strCnn("Provider=sqloledb;Data Source=MyServer;"
            "Initial Catalog=pubs;User Id=sa;Password=;");    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _RecordsetPtr  pRstTitles  = NULL;     try
    {
        // Open recordset for titles table.
        TESTHR(pRstTitles.CreateInstance(__uuidof(Recordset)));
        pRstTitles->CursorLocation = adUseClient;
        pRstTitles->CursorType = adOpenStatic;
        pRstTitles->LockType = adLockBatchOptimistic;
        pRstTitles->Open ("titles",strCnn,
            adOpenStatic, adLockBatchOptimistic, adCmdTable);        // Change the type of the first title in the recordset.
        pRstTitles->Fields->GetItem("type")->Value = 
            (_bstr_t) ("database");        // Display the results of the change.
        printf("\nBefore resync: \n\n");        printf("Title - %s\n\n",(LPSTR) (_bstr_t) pRstTitles->
            Fields->GetItem("title")->Value);        printf("Type - %s\n\n",(LPSTR) (_bstr_t) pRstTitles->
            Fields->GetItem("type")->Value);        // Resync with database.
        pRstTitles->Resync(adAffectAll,adResyncAllValues);        // Display the results of the resynch.
        printf("\n\nAfter resync: \n\n");        printf("Title - %s\n\n",(LPSTR) (_bstr_t) pRstTitles->
            Fields->GetItem("title")->Value);        printf("Type - %s\n\n",(LPSTR) (_bstr_t) pRstTitles->
            Fields->GetItem("type")->Value);        pRstTitles->CancelBatch(adAffectAll);
        pRstTitles->Close();
    }    catch (_com_error &e)
    {
       // Notify the user of errors if any.
       // Pass a connection pointer accessed from the Recordset.
        _variant_t vtConnect = pRstTitles->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 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\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);
}
// EndResyncCppSee Also
Resync Method&copy; 1998-2001 Microsoft Corporation. All rights reserved.