我已关注这篇 MSDN 文章，该文章展示了从本地计算机检索 WMI 数据的示例 http://msdn.microsoft.com/en-us/library/windows/desktop/aa390423%28v=vs.85%29.aspx

显示的示例获取操作系统的名称，但在我的例子中，我正在查询“从 WmiMonitorConnectionParams 选择 *”并想要检索 D3DKMDT_VIDEO_OUTPUT_TECHNOLOGY http://msdn.microsoft.com/en-us/library/windows/hardware/ff546605%28v=vs.85%29.aspx

在这种情况下，我应该如何使用 IWbemClassObject::Get？ VARIANT 变量的哪个成员存储了我想要的结果？

更一般地说，我们应该如何知道每次查询后在 Get 方法中使用哪些标志以及 VARIANT 的哪个成员存储结果？这在哪里记录？

谢谢。

最佳答案

是的，您必须使用 IWbemClassObject检索数据的接口(interface)，关于要使用的变体成员，它取决于 WMI 属性的类型，在本例中为 VideoOutputTechnology property 是一个 uint32 值，因此您必须使用 uintVal 成员。

检查此示例代码

#include "stdafx.h"
#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>
# pragma comment(lib, "wbemuuid.lib")


// Monitor's basic connection parameters

#pragma argsused
int main(int argc, char* argv[])
{
    BSTR strNetworkResource;
    //To use a WMI remote connection set localconn to false and configure the values of the pszName, pszPwd and the name of the remote machine in strNetworkResource
    strNetworkResource = L"\\\\.\\root\\WMI";

    COAUTHIDENTITY *userAcct =  NULL ;
    COAUTHIDENTITY authIdent;

    // Initialize COM. ------------------------------------------

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

    // 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;
        cout << _com_error(hres).ErrorMessage() << endl;
        CoUninitialize();
        cout << "press enter to exit" << endl;
        cin.get();      
        return 1;                    // Program has failed.
    }

    // Obtain the initial locator to WMI -------------------------

    IWbemLocator *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;
        cout << _com_error(hres).ErrorMessage() << endl;
        CoUninitialize();       
        cout << "press enter to exit" << endl;
        cin.get();      
        return 1;                 // Program has failed.
    }

    // Connect to WMI through the IWbemLocator::ConnectServer method

    IWbemServices *pSvc = NULL;

        hres = pLoc->ConnectServer(
             _bstr_t(strNetworkResource),      // 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 (e.g. Kerberos)
             0,                       // Context object
             &pSvc                    // pointer to IWbemServices proxy
             );

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

    cout << "Connected to root\\WMI WMI namespace" << endl;

    // 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;
        cout << _com_error(hres).ErrorMessage() << endl;
        pSvc->Release();
        pLoc->Release();
        CoUninitialize();
        cout << "press enter to exit" << endl;
        cin.get();      
        return 1;               // Program has failed.
    }

    // Use the IWbemServices pointer to make requests of WMI ----

    IEnumWbemClassObject* pEnumerator = NULL;
    hres = pSvc->ExecQuery( L"WQL", L"SELECT * FROM WmiMonitorConnectionParams",
    WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &pEnumerator);

    if (FAILED(hres))
    {
        cout << "ExecQuery failed" << " Error code = 0x"    << hex << hres << endl;
        cout << _com_error(hres).ErrorMessage() << endl;
        pSvc->Release();
        pLoc->Release();
        CoUninitialize();
        cout << "press enter to exit" << endl;
        cin.get();      
        return 1;               // Program has failed.
    }


    // Get the data from the WQL sentence
    IWbemClassObject *pclsObj = NULL;
    ULONG uReturn = 0;

    while (pEnumerator)
    {
        HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1, &pclsObj, &uReturn);

        if(0 == uReturn || FAILED(hr))
          break;

        VARIANT vtProp;

                hr = pclsObj->Get(L"Active", 0, &vtProp, 0, 0);// Boolean
                if (!FAILED(hr))
                {
                  if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
                    wcout << "Active : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
                  else
                    wcout << "Active : " << (vtProp.boolVal ? "True" : "False") << endl;
                }
                VariantClear(&vtProp);

                hr = pclsObj->Get(L"InstanceName", 0, &vtProp, 0, 0);// String
                if (!FAILED(hr))
                {
                  if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
                    wcout << "InstanceName : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
                  else
                    wcout << "InstanceName : " << vtProp.bstrVal << endl;
                }
                VariantClear(&vtProp);

                hr = pclsObj->Get(L"VideoOutputTechnology", 0, &vtProp, 0, 0);// Uint32
                if (!FAILED(hr))
                {
                  if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
                    wcout << "VideoOutputTechnology : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
                  else
                    wcout << "VideoOutputTechnology : " << vtProp.uintVal << endl;
                }
                VariantClear(&vtProp);


        pclsObj->Release();
        pclsObj=NULL;
    }

    // Cleanup

    pSvc->Release();
    pLoc->Release();
    pEnumerator->Release();
    if (pclsObj!=NULL)
     pclsObj->Release();

    CoUninitialize();
    cout << "press enter to exit" << endl;
    cin.get();
    return 0;   // Program successfully completed.
}

您还可以使用类似 wmi delphi code creator 的工具这可以帮助您探索 WMI 并生成 C++ 代码以访问 WMI 数据。

关于c++ - 查询 D3DKMDT_VIDEO_OUTPUT_TECHNOLOGY 的 WMI，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10085900/