(1)_bstr_t 与 CString 相互转换
_bstr_t bstr;
CString strSql;
CString->_bstr_t: bstr = (_bstr_t) strSql;
_bstr_t->CString: strSql = (LPCSTR) bstr;
(2) BSTR 宽字符串与CString相互转换
BSTR bstr;
CString strSql;
CString->BSTR: bstr = strSql.AllocSysString();
BSTR->CString:strSql = (LPCSTR) bstr;