VC下的ADO编程入门(2-3)

在正式进入本主题前，让我们先来看一下COM API编程

#include <windows.h>

#include <objbase.h>

#include <initguid.h>

#include "adoid.h"

#include "adoint.h"

struct InitOle

{

         InitOle(){::CoInitialize(NULL);}

         ~InitOle(){::CoUninitialize();}

}_init_InitOle_;

void main(int argc, char* argv[])

{

         HRESULT hr = S_OK;

         ADORecordset *Rs1 = NULL;

         VARIANT Source;

         VARIANT Connect;

         VariantInit(&Source);

         VariantInit(&Connect);

         Source.vt = VT_BSTR;

         Source.bstrVal = ::SysAllocString(L"SELECT * FROM Customers");

         Connect.vt = VT_BSTR;

         Connect.bstrVal = ::SysAllocString(L"Provider=SQLOLEDB; data source=127.0.0.1;initial catalog=Northwind; user id=sa; password=;");

         hr = CoCreateInstance(CLSID_CADORecordset, NULL, CLSCTX_INPROC_SERVER, IID_IADORecordset, (LPVOID *)&Rs1 );

         if(SUCCEEDED(hr))

         {

                   Rs1->put_CursorLocation(adUseClient);

                   hr = Rs1->Open(Source, Connect, adOpenForwardOnly, adLockReadOnly,-1);

                   long n;

                   Rs1->get_RecordCount(&n);

                   Rs1->Close();

                   Rs1->Release(); Rs1 = NULL;

                   ::MessageBox(NULL, "Success!", "", MB_OK);

                   printf("%d",n);

         }

}

本例完成的功能就是取得数据库中某表的记录数。

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