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Implement GetMethodProperty

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Applies to: yesVisual Studio noVisual Studio for Mac

Note

This article applies to Visual Studio 2017. If you're looking for the latest Visual Studio documentation, see Visual Studio documentation. We recommend upgrading to the latest version of Visual Studio. Download it here

Important

In Visual Studio 2015, this way of implementing expression evaluators is deprecated. For information about implementing CLR expression evaluators, see CLR expression evaluators and Managed expression evaluator sample.

Visual Studio calls the debug engine's (DE) GetDebugProperty, which in turn calls GetMethodProperty to obtain information about the current method on the stack frame.

This implementation of IDebugExpressionEvaluator::GetMethodProperty performs the following tasks:

  1. Calls GetContainerField, passing in the IDebugAddress object. The symbol provider (SP) returns an IDebugContainerField representing the method that contains the specified address.

  2. Obtains the IDebugMethodField from the IDebugContainerField.

  3. Instantiates a class (called CFieldProperty in this example) that implements the IDebugProperty2 interface and contains the IDebugMethodField object returned from the SP.

  4. Returns the IDebugProperty2 interface from the CFieldProperty object.

Managed code

This example shows an implementation of IDebugExpressionEvaluator::GetMethodProperty in managed code.

namespace EEMC
{
    [GuidAttribute("462D4A3D-B257-4AEE-97CD-5918C7531757")]
    public class EEMCClass : IDebugExpressionEvaluator
    {
        public HRESULT GetMethodProperty(
                IDebugSymbolProvider symbolProvider,
                IDebugAddress        address,
                IDebugBinder         binder,
                int                  includeHiddenLocals,
            out IDebugProperty2      property)
        {
            IDebugContainerField containerField = null;
            IDebugMethodField methodField       = null;
            property = null;

            // Get the containing method field.
            symbolProvider.GetContainerField(address, out containerField);
            methodField = (IDebugMethodField) containerField;

            // Return the property of method field.
            property = new CFieldProperty(symbolProvider, address, binder, methodField);
            return COM.S_OK;
        }
    }
}

Unmanaged code

This example shows an implementation of IDebugExpressionEvaluator::GetMethodProperty in unmanaged code.

[CPP]
STDMETHODIMP CExpressionEvaluator::GetMethodProperty(
        in IDebugSymbolProvider *pprovider,
        in IDebugAddress        *paddress,
        in IDebugBinder         *pbinder,
        in BOOL                  includeHiddenLocals,
        out IDebugProperty2    **ppproperty
    )
{
    if (pprovider == NULL)
        return E_INVALIDARG;

    if (ppproperty == NULL)
        return E_INVALIDARG;
    else
        *ppproperty = 0;

    HRESULT hr;
    IDebugContainerField* pcontainer = NULL;

    hr = pprovider->GetContainerField(paddress, &pcontainer);
    if (FAILED(hr))
        return hr;

    IDebugMethodField*    pmethod    = NULL;
    hr = pcontainer->QueryInterface( IID_IDebugMethodField,
            reinterpret_cast<void**>(&pmethod));
    pcontainer->Release();
    if (FAILED(hr))
        return hr;

    CFieldProperty* pfieldProperty = new CFieldProperty( pprovider,
                                                         paddress,
                                                         pbinder,
                                                         pmethod );
    pmethod->Release();
    if (!pfieldProperty)
        return E_OUTOFMEMORY;

    hr = pfieldProperty->Init();
    if (FAILED(hr))
    {
        pfieldProperty->Release();
        return hr;
    }

    hr = pfieldProperty->QueryInterface( IID_IDebugProperty2,
            reinterpret_cast<void**>(ppproperty));
    pfieldProperty->Release();

    return hr;
}

See also