Passing more than one variable to ExecMethod

Question

I am trying to call wmisetbrightness, but it takes two inputs. How do I pass more than one input to ExecMethod? Code snippet below is obviously wrong.

// set up to call the WmiSetBrightness Method
BSTR MethodName = SysAllocString(L"WmiSetBrightness");
BSTR ClassName = SysAllocString(L"WmiMonitorBrightnessMethods");

IWbemClassObject* pClass = NULL;
hres = pSvc->GetObject(ClassName, 0, NULL, &pClass, NULL);

IWbemClassObject* pInParamsDefinition = NULL;
hres = pClass->GetMethod(MethodName, 0, 
    &pInParamsDefinition, NULL);

IWbemClassObject* pClassInstance = NULL;
hres = pInParamsDefinition->SpawnInstance(0, &pClassInstance);

// Create the values for the in parameters
VARIANT varCommand;
varCommand.vt = VT_UI8;
varCommand.ullVal = 30;
//// Store the value for the in parameters
hres = pClassInstance->Put(L"CommandLine", 0, &varCommand, 0);

// Execute Method
IWbemClassObject* pOutParams = NULL;
hres = pSvc->ExecMethod(ClassName, MethodName, 0,
NULL, pClassInstance, &pOutParams, NULL);

edit: WmiSetBrightness takes two variables:

uint32 WmiSetBrightness( uint64 Timeout, uint8 Brightness );

the above code only passes the first input parameter, and I dont know how to modify it to pass both parameters.

Full code here:

#define _WIN32_DCOM

#include <iostream>
using namespace std;
#include <comdef.h>
#include <Wbemidl.h>

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

int main(int iArgCnt, char ** argv)
{
HRESULT hres;

// Step 1: --------------------------------------------------
// Initialize COM. ------------------------------------------

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

// 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 ------------------------

hres =  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
    );


if (FAILED(hres))
{
    cout << "Failed to initialize security. Error code = 0x" 
         << hex << hres << endl;
    CoUninitialize();
    return 1;                      // Program has failed.
}

// Step 3: ---------------------------------------------------
// 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;
    CoUninitialize();
    return 1;                 // Program has failed.
}

// Step 4: ---------------------------------------------------
// Connect to WMI through the IWbemLocator::ConnectServer method

IWbemServices *pSvc = NULL;

// Connect to the local root\cimv2 namespace
// and obtain pointer pSvc to make IWbemServices calls.
hres = pLoc->ConnectServer(
    _bstr_t(L"ROOT\\wmi"), 
    NULL,
    NULL, 
    0, 
    NULL, 
    0, 
    0, 
    &pSvc
);

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

cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


// Step 5: --------------------------------------------------
// Set security levels for 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;
    pSvc->Release();
    pLoc->Release();     
    CoUninitialize();
    return 1;               // Program has failed.
}


///////////////////////////////////////////////////////////////////////////////////////////////////////////////
// set up to call the WmiSetBrightness Method
BSTR MethodName = SysAllocString(L"WmiSetBrightness");
BSTR ClassName = SysAllocString(L"WmiMonitorBrightnessMethods");

IWbemClassObject* pClass = NULL;
hres = pSvc->GetObject(ClassName, 0, NULL, &pClass, NULL);

IWbemClassObject* pInParamsDefinition = NULL;
hres = pClass->GetMethod(MethodName, 0, 
    &pInParamsDefinition, NULL);

IWbemClassObject* pClassInstance = NULL;
hres = pInParamsDefinition->SpawnInstance(0, &pClassInstance);

 VARIANT var1;
 VariantInit(&var1);

 V_VT(&var1) = VT_BSTR;
 V_BSTR(&var1) = SysAllocString(L"0"); 
 hres = pClassInstance->Put(L"Timeout", 0, &var1, CIM_UINT32); //CIM_UINT64

 VARIANT var2;
 VariantInit(&var2);

 V_VT(&var2) = VT_BSTR;
 V_BSTR(&var2) = SysAllocString(L"30"); 
 hres = pClassInstance->Put(L"Brightness", 0, &var2, CIM_UINT8); 

// Execute Method
IWbemClassObject* pOutParams = NULL;
hres = pSvc->ExecMethod(ClassName, MethodName, 0,
NULL, pClassInstance, &pOutParams, NULL);


if (FAILED(hres))
{
    cout << "Could not execute method. Error code = 0x" 
         << hex << hres << endl;
    //VariantClear(&varCommand);
    SysFreeString(ClassName);
    SysFreeString(MethodName);
    pClass->Release();
    pInParamsDefinition->Release();
    pOutParams->Release();
    pSvc->Release();
    pLoc->Release();     
    CoUninitialize();
    return 1;               // Program has failed.
}

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


// Clean up
//--------------------------
// VariantClear(&varCommand);
VariantClear(&varReturnValue);
SysFreeString(ClassName);
SysFreeString(MethodName);
pClass->Release();
pInParamsDefinition->Release();
pOutParams->Release();
pLoc->Release();
pSvc->Release();
CoUninitialize();
return 0;
}

Answer 1

Try this, which supposedly works per info here. Apparently the docs are misleading on this API.

 VARIANT var1;
 VariantInit(&var1);

 V_VT(&var1) = VT_BSTR;
 V_BSTR(&var1) = SysAllocString(L"0"); 
 hr = pClassInstance->Put(L"Timeout", 0, &var1, CIM_UINT32); //CIM_UINT64

 VARIANT var2;
 VariantInit(&var2);

 V_VT(&var2) = VT_BSTR;
 V_BSTR(&var2) = SysAllocString(L"30"); 
 hr = pClassInstance->Put(L"Brightness", 0, &var2, CIM_UINT8); 

Answer 2

I googled by right-clicking stuff in your code and selecting "Search google for...".

That spit out the documentation of SWbemServices.ExecMethod.

Apparently the third argument, where you're specifying 0, can be an SWbemObject specifying the input paramters to the method.

Anyway, study the documentation.

Try things out (perhaps in script first?).

Cheers & hth.