Get WMI Information in C# / Visual C++

I’ve received a couple of comments on the post about finding CPU and Motherboard Info through WMI for providing Visual C++ and VB.NET programs to get WMI information. I’m not a champ at Visual C++ and VB.NET (I usually work with PHP, its about 3 years ago when I worked with C++, C# and VB.NET), but I researched for some working solutions to get this task done for my readers.

I’ve been researching for a C# or C++ program to fetch WMI Information and came across several programs on web but none of them were in the working state, before I received a mail from M Dougann containing a working program for the task.

This article wraps in a working C# / Visual C++ program to get WMI Information, shared by M Dougann.

#define _WIN32_DCOM
#pragma comment(lib, "wbemuuid.lib")

#include <iostream>
#include <string>
#include <stdexcept>
#include <stdlib.h>     // EXIT_FAILURE, EXIT_SUCCESS
using namespace std;

#include lgt;comdef.h>
#include <Wbemidl.h>
#define DEF_SMARTPTR_TYPE( Interface ) \ _COM_SMARTPTR_TYPEDEF( Interface, __uuidof( Interface ) )

DEF_SMARTPTR_TYPE( IWbemLocator );
DEF_SMARTPTR_TYPE( IWbemServices );
DEF_SMARTPTR_TYPE( IWbemClassObject );

bool throwX( string const& s ) { throw std::runtime_error( s ); }

string hexFrom( unsigned long v )
{
    char    buf[40];
    sprintf( buf, "%08lx", v );
    return buf;
}

struct Fail
{
    string  message;
    explicit Fail( string const& aMessage ): message( aMessage ) {}
};

void operator ||( HRESULT hr, Fail const& failure )
{
    SUCCEEDED( hr )
        || throwX( failure.message + " (Error code 0x" + hexFrom( hr ) + ")" );
}

struct ComLibUsage
{
    struct Threading
    {
        enum Enum {
            singleThreaded  = COINIT_APARTMENTTHREADED,
            multiThreaded   = COINIT_MULTITHREADED
        };
    };

    ComLibUsage( Threading::Enum threading = Threading::multiThreaded )
    {
        ::CoInitializeEx( 0, threading )
            || Fail( "Failed to initialize COM library." );
    }

    ~ComLibUsage() { ::CoUninitialize(); }
};

void cppMain()
{
    // Step 1:
    // Initialize COM.
    ComLibUsage     comLibUsage( ComLibUsage::Threading::multiThreaded );

    // Step 2:
    // Set general COM security levels
    // Note: If you are using Windows 2000, you must specify -
    // the default authentication credentials for a user by using
    // a SOLE_AUTHENTICATION_LIST structure in the pAuthList
    // parameter of CoInitializeSecurity
    CoInitializeSecurity(
        NULL, 
        -1,                          // COM negotiates service
        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
        ) || Fail( "Failed to initialize security" );

    // Step 3:
    // Obtain the initial locator to WMI
    IWbemLocatorPtr     pLoc;
    CoCreateInstance(
        CLSID_WbemLocator,             
        0, 
        CLSCTX_INPROC_SERVER, 
        IID_IWbemLocator, (LPVOID *) &pLoc
        ) || Fail( "Failed to create IWbemLocator object." );

    // Step 4:
    // Connect to WMI through the IWbemLocator::ConnectServer method
    // Connect to the local root\cimv2 namespace
    // and obtain pointer pSvc to make IWbemServices calls.
    IWbemServicesPtr    pSvc;
    pLoc->ConnectServer(
        _bstr_t(L"ROOT\\wmi"), 
        NULL,
        NULL, 
        0, 
        NULL, 
        0, 
        0, 
        &pSvc
        ) || Fail( "Could not connect." );
    cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


    // Step 5:
    // Set security levels for the proxy
    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 
        ) || Fail( "Could not set proxy blanket" );

    // set up to call the WmiSetBrightness Method
    _bstr_t     methodName  = L"WmiSetBrightness";
    _bstr_t     className   = L"WmiMonitorBrightnessMethods";

    IWbemClassObjectPtr pClass;
    pSvc->GetObject(className, 0, NULL, &pClass, NULL)
        || Fail( "GetObject(className, ...) failed" );

    IWbemClassObjectPtr pInParamsDefinition;
    pClass->GetMethod(methodName, 0, &pInParamsDefinition, NULL)
        || Fail( "GetMethod(methodName, ...) failed" );

    IWbemClassObjectPtr pClassInstance;
    pInParamsDefinition->SpawnInstance(0, &pClassInstance)
        || Fail( "SpawnInstance failed" );

    _variant_t  var1( L"1000" );
    pClassInstance->Put(L"Timeout", 0, &var1, CIM_UINT32)   //CIM_UINT64
        || Fail( "Put failed for 'Timeout'" );

    _variant_t  var2( L"30" );
    pClassInstance->Put(L"Brightness", 0, &var2, CIM_UINT8)
        || Fail( "Put failed for 'Brightness'" );

    // Execute Method
    IWbemClassObject* pOutParams = NULL;
    //hres = pSvc->ExecMethod(className, methodName, 0,
    //NULL, pClassInstance, &pOutParams, NULL)
        //|| Fail( "Could not execute method" );

    // To see what the method returned,
    // use the following code.  The return value will
    // be in &varReturnValue
    _variant_t varReturnValue;
    pOutParams->Get(_bstr_t(L"ReturnValue"), 0, &varReturnValue, NULL, 0)
        || Fail( "Get failed" );
}

int main()
{
    try
    {
        cppMain();
        return EXIT_SUCCESS;
    }
    catch( exception const& x )
    {
        cerr << "!" << x.what() << endl;
    }
    return EXIT_FAILURE;
}

I hope this article has helped you to obtain WMI Information through C# / C++, feel free to post your queries, I’ll try my best to provide the solutions and fixes.