我已阅读此MSDN文章，其中显示了从本地计算机http://msdn.microsoft.com/en-us/library/windows/desktop/aa390423%28v=vs.85%29.aspx
检索WMI数据的示例显示的示例获取操作系统的名称，但在我的情况下，我查询“从WmiMonitorConnectionParams中选择*”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追求的结果？
更一般地说，我们如何知道每个查询后Get方法中使用哪些标志以及VARIANT的哪个成员存储结果？这记录在哪里？
感谢。
答案 0 :(得分：2)
是的，你必须使用IWbemClassObject接口来检索数据，关于要使用的变体成员，它取决于WMI属性的类型，在这种情况下VideoOutputTechnology属性是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.
}
此外，您可以使用wmi delphi code creator之类的工具来帮助您浏览WMI并生成C ++代码以访问WMI数据。