Hughes Hughes - 1 month ago 44
C++ Question

WMI C++ IWbemServices . ExecMethod for WBEM_E_INVALID_METHOD_PARAMETERS

I used the mechanism of WMI. Through the modification of dsdt.dsl and production of MOF file, I accomplish the custom WMI function by C#. But there is a problem, when I want to use the C++ - MFC to communicate with the MOF file. While the code runs to the IWbemServices . ExecMethod function, it shows the error message: WBEM_E_INVALID_METHOD_PARAMETERS(0x8004102F). I think the reason occurs with the input parameter: boolean… Hope everyone can provide some suggestions!
Many thanks!

acpimof.mof:

class WMIEvent : __ExtrinsicEvent
{
};

[WMI,
Dynamic,
Provider("WmiProv"),
Locale("MS\\0x409"),
Description("Acpi_Commands"),
guid("{ABBC0F6D-8EA1-11d1-00A0-C90629100000}")
]
class Acpi_Commands
{
[key, read]
string InstanceName;
[read] boolean Active;

[WmiMethodId(1),
Implemented,
read, write,
Description("setReadLight")]
void setReadLight([in, Description("Status")] boolean Status);
};


acpi.cpp:

Copy the MSDN – Example: Calling a Provider Method (https://msdn.microsoft.com/en-us/library/aa390421(v=vs.85).aspx ). The Step 1, 2, 3 & 5 are same totally with the example, so I don’t show the code. I modify the Step 4 & 6.

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

IWbemServices *pSvc = NULL;

// Connect to the local 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.
}


// Step 6: --------------------------------------------------
// Use the IWbemServices pointer to make requests of WMI ----

// set up to call the Win32_Process::Create method
BSTR ClassName = SysAllocString(L"Acpi_Commands");
BSTR MethodName = SysAllocString(L"setReadLight");

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_BOOL;
varCommand.boolVal = VARIANT_TRUE;

// Store the value for the in parameters
hres = pClassInstance->Put(L"Status", 0, &varCommand, CIM_BOOLEAN);

// Execute Method
IWbemClassObject* pOutParams = NULL;
hres = pSvc->ExecMethod(ClassName, MethodName, 0, NULL, pClassInstance, &pOutParams, NULL);
//Get error message: WBEM_E_INVALID_METHOD_PARAMETERS(0x8004102f)

if (FAILED(hres))
{
cout << "Could not execute method. Error code = 0x" << hex << hres << endl;
// Clean up(don't show here)
return 1; // Program has failed.
}

// Clean up(don't show here)

system("pause");
return 0;

Answer

I found the solution by myself, and I share this for someone who needs:)

The issue occurs in the first parameter for the IWbemServices::ExecMethod which needs the specified property value rather than the simple class name. So it needs some setting to get the specified property value.(But the "Example: Calling a Provider Method" only sets the class name for the parameter and it works... I guess the reason happen in the namesapce(original: "ROOT\CIMV2" => that is a standard model for Windows), and I use the "ROOT\WMI" to connect with the WMI, so it needs specified property value. If I'm wrong, please correct me!)

Please revise the Step 6 of the acpi.cpp above.

// Step 6: --------------------------------------------------
// Use the IWbemServices pointer to make requests of WMI ----
BSTR ClassName = SysAllocString(L"Acpi_Commands");
BSTR MethodName = SysAllocString(L"setReadLight");
BSTR bstrQuery = SysAllocString(L"Select * from Acpi_Commands");

//The IEnumWbemClassObject interface is used to enumerate Common Information Model (CIM) objects 
//and is similar to a standard COM enumerator.
IEnumWbemClassObject *pEnum = NULL;
   hres = pSvc->ExecQuery(_bstr_t(L"WQL"), //Query Language
   bstrQuery, //Query to Execute  
   WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, //Make a semi-synchronous call  
   NULL, //Context  
   &pEnum /*Enumeration Interface*/);

hres = WBEM_S_NO_ERROR;

ULONG ulReturned;
IWbemClassObject *pObj;
DWORD retVal = 0;

//Get the Next Object from the collection  
hres = pEnum->Next(WBEM_INFINITE, //Timeout  
    1, //One of object requested  
    &pObj, //Returned Object  
    &ulReturned /*No of object returned*/);

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);
BSTR ArgName0 = SysAllocString(L"Status");

V_VT(&var1) = VT_BOOL;
V_BOOL(&var1) = VARIANT_FALSE;

hres = pClassInstance->Put(ArgName0, 0, &var1, CIM_BOOLEAN);  
printf("\nPut ArgName0 returned 0x%x:", hres);
VariantClear(&var1);

// Call the method  
VARIANT pathVariable;
VariantInit(&pathVariable);

//The IWbemClassObject::Get method retrieves the specified property value, if it exists.
hres = pObj->Get(_bstr_t(L"__PATH"),
    0,
    &pathVariable,
    NULL,
    NULL);
printf("\npObj Get returned 0x%x:", hres);

hres = pSvc->ExecMethod(pathVariable.bstrVal,
    MethodName,
    0,
    NULL,
    pClassInstance,
    NULL,
    NULL);
VariantClear(&pathVariable);
printf("\nExecMethod returned 0x%x:", hres);

printf("Terminating normally\n");


// Clean up
SysFreeString(ClassName);
SysFreeString(MethodName);
pClass->Release();
pClassInstance->Release();
pInParamsDefinition->Release();
pLoc->Release();
pSvc->Release();
CoUninitialize();

system("pause");
return 0;
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