无法在 WMI (c++) 中检索对象属性 [英] Failed to retrieve object property in WMI (c++)

问题描述

我想用 WMI 做一些事情(接收一些事件通知)，所以我从 MSDN 网站上的简单示例开始:

I want to do something with WMI (receiving some event notification) so I start with simple example from MSDN website:

通过接收事件通知WMI

本程序通过WMI接收事件通知(进程创建)，并在接收到事件后调用函数EventSink::Indicate.

this program receives an event notification (process creation) through WMI, and calls the function EventSink::Indicate upon receiving the event.

我在上面的链接(复制/过去)中使用了相同的代码，但做了一个更改:在类 EventSink 中，函数

I used the same code in the link above (copy/past) with one change: in the class EventSink, the function

HRESULT EventSink::Indicate(long lObjectCount, IWbemClassObject **apObjArray)

我添加了几行来检索对象的属性(对象在 apObjArray 中返回):

I added few lines to retrieve a property of the object (the object is returned in apObjArray):

 for (int i = 0; i < lObjectCount; i++)
    {
        VARIANT varName;
        hres = apObjArray[i]->Get(_bstr_t(L"Name"),
            0, &varName, 0, 0);
//...
    }

现在，无论我寻找什么，Get(...) 函数都会返回 WBEM_E_NOT_FOUND(未找到指定的属性)(从文档中可以确定属性在那里...)

now the Get(...) functions returns WBEM_E_NOT_FOUND (The specified property is not found) no matter what I look for (am sure from the documentation that the properties are there...)

请让我知道我错过了什么?！任何帮助表示赞赏.

please let me know what have I missed ?! any help is appreciated.

推荐答案

Name 属性是 TargetInstance 对象的一部分，因此必须获取 TargetInstance 的值对象，然后检索 Name 属性的值.

The Name property is part of the TargetInstance object, so you must get the value of the TargetInstance object and then retrieve the value of the Name property.

试试这个样本

HRESULT EventSink::Indicate(long lObjectCount,
    IWbemClassObject **apObjArray)
{
   HRESULT hr = S_OK;
   _variant_t vtProp;

    for (int i = 0; i < lObjectCount; i++)
    {

    hr = apObjArray[i]->Get(_bstr_t(L"TargetInstance"), 0, &vtProp, 0, 0);
     if (!FAILED(hr))
     {
       IUnknown* str = vtProp;
       hr = str->QueryInterface( IID_IWbemClassObject, reinterpret_cast< void** >( &apObjArray[i] ) );
       if ( SUCCEEDED( hr ) )
       {
          _variant_t cn;
         hr = apObjArray[i]->Get( L"Name", 0, &cn, NULL, NULL );
          if ( SUCCEEDED( hr ) )
          {
            if ((cn.vt==VT_NULL) || (cn.vt==VT_EMPTY))
             wcout << "Name : " << ((cn.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
            else
             wcout << "Name : " << cn.bstrVal << endl;
          }
          VariantClear(&cn);


       }
     }
     VariantClear(&vtProp);

    }

    return WBEM_S_NO_ERROR;
}

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