WMI C ++从对象获取数据

Question

我实施了1-5步骤： https://msdn.microsoft.com/en-us/library/aa390423(v=vs.85).aspx Everyting有效，但是我从查询对象中获取数据时遇到问题。

我的代码：

// Step 1: --------------------------------------------------
// Initialize COM. ------------------------------------------

hres =  CoInitializeEx(0, COINIT_MULTITHREADED); 
if (FAILED(hres))
{
    //cout << "Failed to initialize COM library. Error code = 0x" 
    //    << hex << hres << endl;
    return 1;                  // Program has failed.
}

// Step 2: --------------------------------------------------
// Set general COM security levels --------------------------

hres =  CoInitializeSecurity(
    NULL, 
    -1,                          // COM authentication
    NULL,                        // Authentication services
    NULL,                        // Reserved
    RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication 
    RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation  
    NULL,                        // Authentication info
    EOAC_NONE,                   // Additional capabilities 
    NULL                         // Reserved
    );


if (FAILED(hres))
{
    //cout << "Failed to initialize security. Error code = 0x" 
    //    << hex << hres << endl;
    CoUninitialize();
    return 1;                    // Program has failed.
}

// Step 3: ---------------------------------------------------
// Obtain the initial locator to WMI -------------------------
pLoc = NULL;

hres = CoCreateInstance(
    CLSID_WbemLocator,             
    0, 
    CLSCTX_INPROC_SERVER, 
    IID_IWbemLocator, (LPVOID *) &pLoc);

if (FAILED(hres))
{
    //cout << "Failed to create IWbemLocator object."
    //    << " Err code = 0x"
    //    << hex << hres << endl;
    CoUninitialize();
    return 1;                 // Program has failed.
}

// Step 4: -----------------------------------------------------
// Connect to WMI through the IWbemLocator::ConnectServer method
pSvc = NULL;

// Connect to the root\cimv2 namespace with
// the current user and obtain pointer pSvc
// to make IWbemServices calls.
hres = pLoc->ConnectServer(
     _bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
     NULL,                    // User name. NULL = current user
     NULL,                    // User password. NULL = current
     0,                       // Locale. NULL indicates current
     NULL,                    // Security flags.
     0,                       // Authority (for example, Kerberos)
     0,                       // Context object 
     &pSvc                    // pointer to IWbemServices proxy
     );

if (FAILED(hres))
{
    //cout << "Could not connect. Error code = 0x" 
    //     << hex << hres << endl;
    pLoc->Release();     
    CoUninitialize();
    return 1;                // Program has failed.
}

//OutputDebugString("Connected to ROOT\\CIMV2 WMI namespace");
// Step 5: --------------------------------------------------
// Set security levels on the proxy -------------------------

hres = CoSetProxyBlanket(
   pSvc,                        // Indicates the proxy to set
   RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
   RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
   NULL,                        // Server principal name 
   RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx 
   RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
   NULL,                        // client identity
   EOAC_NONE                    // proxy capabilities 
);

if (FAILED(hres))
{
    cout << "Could not set proxy blanket. Error code = 0x" 
        << hex << hres << endl;
    pSvc->Release();
    pLoc->Release();     
    CoUninitialize();
    return 1;               // Program has failed.
}

上面的代码与msdn示例相同。

问题出在这里：

// Get the currently inserted USB devices
IEnumWbemClassObject* pEnumerator = NULL;
hres = pSvc->ExecQuery(
    bstr_t("WQL"), 
    bstr_t("SELECT * FROM Win32_USBControllerDevice"),
    WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, 
    NULL,
    &pEnumerator);

if (FAILED(hres))
{
    //cout << "Query for USB devices at startup failed."
    //    << " Error code = 0x" 
    //    << hex << hres << endl;
    pSvc->Release();
    pLoc->Release();
    CoUninitialize();
    return 1;               // Program has failed.
}

// Get the data from the query 
IWbemClassObject *pclsObj = NULL;
ULONG uReturn = 0;   
ostringstream os;
while (pEnumerator){
    HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, 
        &pclsObj, &uReturn);
    if(0 == uReturn){
        break;
    }
    VARIANT vtProp;
    VariantInit(&vtProp);
    // Get the value of the accessstate property
    hr = pclsObj->Get(L"Dependent", 0, &vtProp, 0, 0);
    if (FAILED(hr)){        
        pSvc->Release();
        pLoc->Release();
        CoUninitialize();
        return 1;               // Program has failed.
    }
    os.str("");
    os.clear();
    os << vtProp.bstrVal;
    OutputDebugString(os.str().c_str());
    AddDevice(os.str());//Add device to devices vector
    VariantClear(&vtProp);  
    pclsObj->Release();
}

正好在这个地方：

hr = pclsObj->Get(L"Dependent", 0, &vtProp, 0, 0);

此链接描述表格元素： https://msdn.microsoft.com/en-us/library/aa394505(v=vs.85).aspx 所以我得到了附属价值。我的问题是如何获得这个从属属性： https://msdn.microsoft.com/en-us/library/aa387884(v=vs.85).aspx 例如：DeviceID 如果有人能帮忙，我将非常感激！