A WMI Wrapper for C++… Easy !

Imagine you want to explore the world of WMI with C++ like that:

 ManagementClass mc(_TEXT("Win32_NetworkAdapter"));
 bool result = mc.GetInstances();
 while (mc.MoveNext())
 {
  CNetworkCard card;
  card.m_Name = mc.GetStringProperty(_TEXT("Name"));
  card.m_MACAddress = mc.GetStringProperty(_TEXT("MACAddress"));
  card.m_Speed = mc.GetStringProperty(_TEXT("Speed"));
  m_data.m_NetworkCards.Add(card);
 }

Here is the class you need:

class ManagementClass
{
public:
ManagementClass(const CString& adr);
~ManagementClass();

bool GetInstances();
bool MoveNext();
CString GetStringProperty(CString propName);
bool GetBoolProperty(CString propName);
int GetIntProperty(CString propName);
long GetLongProperty(CString propName);

protected:
CString m_wmiAdr;
IWbemLocator *m_pLoc;
CComPtr<IWbemServices> m_pSvc;
CComPtr<IEnumWbemClassObject> m_pEnumerator;
CComPtr<IWbemClassObject> m_pclsObj;
};

The implementation is a little by tricky. Look:

#include "stdafx.h"
#include "ManagementClass.h"
ManagementClass::ManagementClass(const CString& adr)
{
m_wmiAdr.Format(_TEXT("SELECT * From %s"), adr);
m_pLoc = nullptr;
m_pEnumerator = nullptr;
m_pclsObj = nullptr;
}
ManagementClass::~ManagementClass()
{
if (m_pLoc)
{
m_pLoc->Release();
m_pLoc = nullptr;
}
}

bool ManagementClass::GetInstances()
{
static bool bSecurity = false;

HRESULT hres;

if (bSecurity == false)
{
bSecurity = true;

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
);
}

hres = CoCreateInstance(
CLSID_WbemLocator,
0,
CLSCTX_INPROC_SERVER,
IID_IWbemLocator, (LPVOID *)&m_pLoc);
if (FAILED(hres))
{
return false;
}

// Connect to WMI through the IWbemLocator::ConnectServer method
// Connect to the root\cimv2 namespace with
// the current user and obtain pointer pSvc
// to make IWbemServices calls.
hres = m_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 (e.g. Kerberos)
0,                       // Context object
&m_pSvc                    // pointer to IWbemServices proxy
);

if (FAILED(hres))
{
m_pLoc->Release();
return false;                // Program has failed.
}

hres = CoSetProxyBlanket(
m_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))
{
m_pLoc->Release();
return false;
}

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

// For example, get the name of the operating system
//IEnumWbemClassObject* pEnumerator = NULL;
//CComPtr<IEnumWbemClassObject> pEnumerator = NULL;
hres = m_pSvc->ExecQuery(
bstr_t("WQL"),
bstr_t((LPTSTR)(LPCTSTR)m_wmiAdr),
WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
NULL,
&m_pEnumerator);

if (m_pEnumerator == NULL)
{
return false;
}

if (FAILED(hres))
{
m_pLoc->Release();
return false;
}

return true;
}

bool ManagementClass::MoveNext()
{
ULONG uReturn = 0;
if (m_pEnumerator)
{
CComPtr<IWbemClassObject> pclsObj = nullptr;
HRESULT hr = m_pEnumerator->Next(WBEM_INFINITE, 1, &pclsObj, &uReturn);
if (hr == S_FALSE)
{
return false;
}

m_pclsObj = pclsObj;
}
else
{
return false;
}

return true;
}

CString ManagementClass::GetStringProperty(CString propName)
{
ASSERT(m_pclsObj != NULL);
CComVariant vtProp;
HRESULT hr = m_pclsObj->Get(propName, 0, &vtProp, 0, 0);
CString data;
AfxBSTR2CString(&data, vtProp.bstrVal);
return data;
}

bool ManagementClass::GetBoolProperty(CString propName)
{
ASSERT(m_pclsObj != NULL);
bool result = false;
CComVariant vtProp;
HRESULT hr = m_pclsObj->Get(propName, 0, &vtProp, 0, 0);
if (vtProp.boolVal == 1)
result = true;
return result;
}

int ManagementClass::GetIntProperty(CString propName)
{
ASSERT(m_pclsObj != NULL);
CComVariant vtProp;
HRESULT hr = m_pclsObj->Get(propName, 0, &vtProp, 0, 0);
int i = vtProp.iVal;
return i;
}

long ManagementClass::GetLongProperty(CString propName)
{
ASSERT(m_pclsObj != NULL);
CComVariant vtProp;
HRESULT hr = m_pclsObj->Get(propName, 0, &vtProp, 0, 0);
long l = vtProp.lVal;
return l;
}

Don’t forget the include stuff in the stdafx.h:

#include <Wbemidl.h>

#pragma comment(lib, “wbemuuid.lib”)

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Tagged: C++, COM, WMI