VC调用存储过程的通用方法（SQLServer篇）

这里讨论的是ADO调用存储过程，按MSDN的例子，一般都是下面的调用方法（节选自MSDN）：
HRESULT hr = S_OK;
    // Define ADO object pointers.
    // Initialize pointers on define.
    // These are in the ADODB::  namespace.
    _RecordsetPtr pRstByRoyalty = NULL;
    _RecordsetPtr pRstAuthors = NULL; 
    _CommandPtr   pcmdByRoyalty = NULL;
    _ParameterPtr pprmByRoyalty = NULL;
    _ConnectionPtr pConnection = NULL;
    _bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
        "Initial Catalog=Pubs;User Id=sa;Password=;");
    _bstr_t strMessage, strAuthorID;
    int intRoyalty;
    VARIANT vtRoyalty;
    try
    {
        //Open a Connection.
        TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
        hr = pConnection->Open(strCnn,"","",NULL);
        pConnection->CursorLocation = adUseClient;
        //Open Command Object with one Parameter
        TESTHR(pcmdByRoyalty.CreateInstance(__uuidof(Command)));
        pcmdByRoyalty->CommandText = "byroyalty";
        pcmdByRoyalty->CommandType = adCmdStoredProc;
        //Define Integer/variant.
        vtRoyalty.vt = VT_I2;
        vtRoyalty.iVal = intRoyalty;
        pprmByRoyalty = pcmdByRoyalty->CreateParameter(
            "percentag