VC中调用ADO对象访问数据库的范例

Visual C++ Code #include "stdafx.h" #include "stdio.h" #include "windows.h" #include "string.h" #import "C:/Program Files/Common Files/System/ado/msado20.tlb" no_namespace rename("EOF", "adoEOF") HRESULT ComInit(); int APIENTRY WinMain(HINSTANCE hInstance,                      HINSTANCE hPrevInstance,                      LPSTR     lpCmdLine,                      int       nCmdShow) {     _ConnectionPtr pCn;     _RecordsetPtr pRs;     _variant_t vtEmpty;     _variant_t vRsinfo;     long ccc;     char jj[255];     int j;     ComInit();     pCn.CreateInstance(__uuidof(Connection));     pRs.CreateInstance(__uuidof(Recordset));     pCn->Open("DRIVER={Microsoft Access Driver (*.mdb)};DBQ=C://VcADO//users.mdb","","",-1);     if(pCn->State==0){         MessageBox(0,"连接数据库失败。","连接失败",MB_OK);     }else{         vtEmpty="select * from 用户信息表";         pRs->Open(vtEmpty, pCn.GetInterfacePtr(),adOpenStatic,adLockOptimistic,adCmdText);         ccc=pRs->RecordCount;         if(ccc>=1){             vRsinfo=pRs->Fields->GetItem("姓名")->GetValue();             j=sprintf(jj,"查询到:%s",(char*)(_bstr_t)vRsinfo);             MessageBox(0,jj,"查询成功",MB_OK);             pRs->Close();         }else{             MessageBox(0,"没有查询到数据.","查询失败",MB_OK);         }         pCn->Close();     }     return 0; } //COM 使用时初始化 HRESULT ComInit() {     HRESULT hr = S_OK;             // 默认返回值     if FAILED(CoInitialize(NULL))  // COM 初始化调用     {         CoUninitialize();         hr = E_UNEXPECTED;     }     return hr; }