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Getting Local Properties

Visual Studio calls IDebugProperty2::EnumChildren to obtain an IEnumDebugPropertyInfo2 object that provides access to all the locals to be displayed in the Locals window. Visual Studio then calls IEnumDebugPropertyInfo2::Next to get the information to be displayed for each local. In this example, the class CEnumPropertyInfo implements the IEnumDebugPropertyInfo2 interface.

This implementation of IEnumDebugPropertyInfo2::Next performs the following tasks:

  1. Clears the array where the information is to be stored.

  2. Calls IEnumDebugFields::Next for each local, storing the returned DEBUG_PROPERTY_INFO in the array to be returned. The IEnumDebugFields object was supplied when this CEnumPropertyInfo class was instantiated.

Managed Code

This example shows an implementation of IEnumDebugPropertyInfo2::EnumChildren for a method's locals in managed code.

namespace EEMC
{
    public class CEnumMethodField : IEnumDebugFields
    {
        public HRESULT Next(
                uint                  count,
                DEBUG_PROPERTY_INFO[] properties,
            out uint                  fetched)
        {
            if (count > properties.Length)
                throw new COMException();

            // Zero out the array.
            for (int i= 0; i < count; i++)
            {
                properties[i].bstrFullName = "";
                properties[i].bstrName = "";
                properties[i].bstrType = "";
                properties[i].bstrValue = "";
                properties[i].dwAttrib = 0;
                properties[i].dwFields = 0;
                properties[i].pProperty = null;
            }
            fetched = 0;

            // COM interop.
            HRESULT hr;
            uint innerFetched;
            IDebugField[] field = new IDebugField[1];

            while (fetched < count)
            {
                field[0] = null;
                innerFetched = 0;

                // Get next field.
                if (fetched < fieldCount)
                    hr = fields.Next(1, field, ref innerFetched);
                // No more fields.
                else return COM.S_FALSE;

                if (hr != COM.S_OK || innerFetched != 1 || field[0] == null)
                    throw new COMException("CEnumPropertyInfo.Next");

                // Get property from field.
                CFieldProperty fieldProperty = 
                    new CFieldProperty(provider, address, binder, field[0]);

                DEBUG_PROPERTY_INFO[] property =
                                new DEBUG_PROPERTY_INFO[1];
                fieldProperty.GetPropertyInfo((uint) infoFlags, radix, 0, null, 0, property);
                properties[fetched++] = property[0];
            }
            return COM.S_OK;
        }
    }
}

Unmanaged Code

This example shows an implementation of IEnumDebugPropertyInfo2::EnumChildren for a method's locals in unmanaged code.

STDMETHODIMP CEnumPropertyInfo::Next(
    in  ULONG                count,
    out DEBUG_PROPERTY_INFO* pelements, 
    out ULONG*               pfetched )
{
    if (pfetched)
        *pfetched = 0;
    if (!pelements)
        return E_INVALIDARG;
    else
        memset( pelements, 0, count * sizeof(DEBUG_PROPERTY_INFO));

    HRESULT hr  = S_OK;
    ULONG   idx = 0;
    while (idx < count)
    {
        ULONG        fetchedFields;
        IDebugField* pfield;

        //get the next field
        hr = m_fields->Next( 1, &pfield, &fetchedFields );
        if (FAILED(hr))
            return hr;
        if (fetchedFields != 1)
            return E_FAIL;
        idx++;

        //create a CFieldProperty to retrieve the DEBUG_PROPERTY_INFO
        CFieldProperty* pproperty =
            new CFieldProperty( m_provider, m_address, m_binder, pfield );
        pfield->Release();
        if (!pproperty)
            return E_OUTOFMEMORY;

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

        hr = pproperty->GetPropertyInfo( m_infoFlags,
                                         m_radix,
                                         0,
                                         NULL,
                                         0,
                                         pelements + idx - 1);
        pproperty->Release();
        if (FAILED(hr))
            return hr;
    }

    if (pfetched)
        *pfetched = idx;
    return hr;
}

See Also

Concepts

Sample Implementation of Locals

Enumerating Locals