如何在C++中使用WMI从WIN32_NetworkAdapter中检索值?我无法理解用于在查询后访问值的VARIANT

MSDN有很多关于WMI and C++的资源。此外，如果您是从C++使用WMI的新手，您可以使用WMI Delphi Code Creator，它允许您生成C++代码来访问WMI类、事件和方法。

试试这个由应用程序生成的示例代码

#include "stdafx.h"
#define _WIN32_DCOM
#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>
#pragma comment(lib, "wbemuuid.lib")
//CREDENTIAL structure
//http://msdn.microsoft.com/en-us/library/windows/desktop/aa374788%28v=vs.85%29.aspx
#define CRED_MAX_USERNAME_LENGTH            513
#define CRED_MAX_CREDENTIAL_BLOB_SIZE       512
#define CREDUI_MAX_USERNAME_LENGTH CRED_MAX_USERNAME_LENGTH
#define CREDUI_MAX_PASSWORD_LENGTH (CRED_MAX_CREDENTIAL_BLOB_SIZE / 2)

#pragma argsused
int main(int argc, char* argv[])
{
wchar_t pszName[CREDUI_MAX_USERNAME_LENGTH+1] = L"user";
wchar_t pszPwd[CREDUI_MAX_PASSWORD_LENGTH+1]  = L"password";
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
bool localconn = true;  
strNetworkResource = localconn ?  L"\\.\root\CIMV2" : L"\\remote--machine\root\CIMV2";
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 --------------------------
if (localconn)
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
);
else
hres =  CoInitializeSecurity(
NULL,
-1,                          // COM authentication
NULL,                        // Authentication services
NULL,                        // Reserved
RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication
RPC_C_IMP_LEVEL_IDENTIFY,    // 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;
if (localconn)  
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
);
else
hres = pLoc->ConnectServer(
_bstr_t(strNetworkResource),  // Object path of WMI namespace
_bstr_t(pszName),             // User name
_bstr_t(pszPwd),              // User password
NULL,                // Locale
NULL,                // Security flags
NULL,                // Authority
NULL,                // Context object
&pSvc                // 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\CIMV2 WMI namespace" << endl;
// Set security levels on the proxy -------------------------
if (localconn)
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
);
else
{
// Create COAUTHIDENTITY that can be used for setting security on proxy
memset(&authIdent, 0, sizeof(COAUTHIDENTITY));
authIdent.PasswordLength = wcslen (pszPwd);
authIdent.Password = (USHORT*)pszPwd;
authIdent.User = (USHORT*)pszName;
authIdent.UserLength = wcslen(pszName);
authIdent.Domain = 0;
authIdent.DomainLength = 0;
authIdent.Flags = SEC_WINNT_AUTH_IDENTITY_UNICODE;
userAcct = &authIdent;
hres = CoSetProxyBlanket(
pSvc,                           // Indicates the proxy to set
RPC_C_AUTHN_DEFAULT,            // RPC_C_AUTHN_xxx
RPC_C_AUTHZ_DEFAULT,            // RPC_C_AUTHZ_xxx
COLE_DEFAULT_PRINCIPAL,         // Server principal name
RPC_C_AUTHN_LEVEL_PKT_PRIVACY,  // RPC_C_AUTHN_LEVEL_xxx
RPC_C_IMP_LEVEL_IMPERSONATE,    // RPC_C_IMP_LEVEL_xxx
userAcct,                       // 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 Win32_NetworkAdapter",
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.
}
// Secure the enumerator proxy
if (!localconn)
{
hres = CoSetProxyBlanket(
pEnumerator,                    // Indicates the proxy to set
RPC_C_AUTHN_DEFAULT,            // RPC_C_AUTHN_xxx
RPC_C_AUTHZ_DEFAULT,            // RPC_C_AUTHZ_xxx
COLE_DEFAULT_PRINCIPAL,         // Server principal name
RPC_C_AUTHN_LEVEL_PKT_PRIVACY,  // RPC_C_AUTHN_LEVEL_xxx
RPC_C_IMP_LEVEL_IMPERSONATE,    // RPC_C_IMP_LEVEL_xxx
userAcct,                       // client identity
EOAC_NONE                       // proxy capabilities
);
if (FAILED(hres))
{
cout << "Could not set proxy blanket on enumerator. Error code = 0x" << hex << hres << endl;
cout << _com_error(hres).ErrorMessage() << endl;
pEnumerator->Release();
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"AdapterType", 0, &vtProp, 0, 0);// String
if (!FAILED(hr))
{
if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
wcout << "AdapterType : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
else
wcout << "AdapterType : " << vtProp.bstrVal << endl;
}
VariantClear(&vtProp);
hr = pclsObj->Get(L"AdapterTypeId", 0, &vtProp, 0, 0);// Uint16
if (!FAILED(hr))
{
if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
wcout << "AdapterTypeId : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
else
wcout << "AdapterTypeId : " << vtProp.uiVal << endl;
}
VariantClear(&vtProp);
hr = pclsObj->Get(L"Caption", 0, &vtProp, 0, 0);// String
if (!FAILED(hr))
{
if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
wcout << "Caption : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
else
wcout << "Caption : " << vtProp.bstrVal << endl;
}
VariantClear(&vtProp);
hr = pclsObj->Get(L"Description", 0, &vtProp, 0, 0);// String
if (!FAILED(hr))
{
if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
wcout << "Description : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
else
wcout << "Description : " << vtProp.bstrVal << endl;
}
VariantClear(&vtProp);
hr = pclsObj->Get(L"MACAddress", 0, &vtProp, 0, 0);// String
if (!FAILED(hr))
{
if ((vtProp.vt==VT_NULL) || (vtProp.vt==VT_EMPTY))
wcout << "MACAddress : " << ((vtProp.vt==VT_NULL) ? "NULL" : "EMPTY") << endl;
else
wcout << "MACAddress : " << vtProp.bstrVal << 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.
}

查询返回IEnumWbemClassObject接口的实例。您可以使用它来枚举对象。对象作为IWbemClassObject实例返回。然后，可以使用IWbemClassObject::Get方法来获取属性。

请参阅此MSDN示例；然而，我通常使用CComPtr<>ATL类而不是原始接口指针，与CComVariant和原始VARIANT相同。