在 C++ 中从 WMI 中的 OUT 参数获取值 [英] Getting value from an OUT parameter in WMI in C++

问题描述

我正在尝试使用 WMI 读取注册表值.这是我现在所拥有的:

I am trying to read a registry value using WMI. Here is what I have now:

    BSTR methodName = SysAllocString(L"GetStringValue");
    BSTR className = SysAllocString(L"StdRegProv");
    IWbemClassObject* pInParamsDefinition = nullptr;

    std::wstring errStr = L"ERROR";

    HRESULT hRes = p_regWbemClassObj->GetMethod(methodName, 0, &pInParamsDefinition, NULL);

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

    // Create the values for the in parameters
    VARIANT sSubKeyName;
    sSubKeyName.vt = VT_BSTR;
    sSubKeyName.bstrVal = BSTR(path.c_str());
    VARIANT sValueName;
    sValueName.vt = VT_BSTR;
    sValueName.bstrVal = BSTR(key.c_str());


    // Store the value for the in parameters
    hRes = pClassInstance->Put(L"sSubKeyName", 0,
        &sSubKeyName, 0);
    hRes = pClassInstance->Put(L"sValueName", 0,
        &sSubKeyName, 0);

    // Execute Method
    IWbemClassObject* pOutParams = NULL;
    hRes = p_defWbemServices->ExecMethod(className, methodName, 0,
        NULL, pClassInstance, &pOutParams, NULL);

    if (FAILED(hRes))
    {
        VariantClear(&sSubKeyName);
        VariantClear(&sValueName);
        SysFreeString(className);
        SysFreeString(methodName);
        pInParamsDefinition->Release();
        pClassInstance->Release();
        pOutParams->Release();
        return errStr;
    }


    VARIANT varReturnValue;
    hRes = pOutParams->Get(BSTR(L"sValue"), 0, &varReturnValue, NULL, NULL);

    std::wstring result = varReturnValue.bstrVal;

出于某种原因，我从未得到正确的 varReturnValue.这是函数:http://msdn.microsoft.com/en-us/library/aa390788(v=vs.85).aspx

For some reason I never get a correct varReturnValue. Here is the function: http://msdn.microsoft.com/en-us/library/aa390788(v=vs.85).aspx

推荐答案

您在sSubKeyName"和sValueName"中输入了相同的值 - &sSubKeyName.

You put in "sSubKeyName" and "sValueName" the same value - &sSubKeyName.

// Store the value for the in parameters
    hRes = pClassInstance->Put(L"sSubKeyName", 0,
        &sSubKeyName, 0); // <-- sSubKeyName
    hRes = pClassInstance->Put(L"sValueName", 0,
        &sSubKeyName, 0); // <-- sSubKeyName

我认为你是想这样做:

// Store the value for the in parameters
        hRes = pClassInstance->Put(L"sSubKeyName", 0,
            &sSubKeyName, 0); // <-- sSubKeyName
        hRes = pClassInstance->Put(L"sValueName", 0,
            &sValueName, 0); // <-- sValueName

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