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IDebugHostEvaluator::EvaluateExtendedExpression method (dbgmodel.h)

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The EvaluateExtendedExpression method is similar to the EvaluateExpression method except that it turns back on additional non-language functionality which a particular debug host chooses to add to its expression evaluator. For Debugging Tools for Windows, for example, this enables anonymous types, LINQ queries, module qualifiers, format specifiers, and other non-C/C++ functionality.

It is important to note that there is no guarantee that an expression which evaluates against one host via EvaluateExtendedExpression will evaluate correctly against another host which debugs the same language. Extensions in the expression evaluator are the purview of a given host. It is strongly recommended that clients utilize the EvaluateExpression method instead of the EvaluateExtendedExpression method for this exact reason. Using this method reduces the portability of the caller.

Syntax

HRESULT EvaluateExtendedExpression(
  IDebugHostContext           *context,
  PCWSTR                      expression,
  IModelObject                *bindingContext,
  _COM_Errorptr_ IModelObject **result,
  IKeyStore                   **metadata
);

Parameters

context

The host context in which the expression evaluation occurs. If there are, for instance, memory reads of the target due to pointer dereferences, the address space in which those memory reads are made is given by this argument.

expression

The expression to be evaluated. This may use host private extensions to the language syntax.

bindingContext

The binding context in which symbol (variable) names will be looked up. For C++, this is semantically equivalent to the this pointer value.

result

The resulting value of the expression evaluation will be returned here.

metadata

Any metadata associated with the expression or result is returned here.

Return value

This method returns HRESULT which indicates success or failure.

Remarks

Code Sample

ComPtr<IDebugHost> spHost; /* get the host */

ComPtr<IDebugHostEvaluator> spEval;
if (SUCCEEDED(spHost.As(&spEval)))
{
    ComPtr<IModelObject> spNotepadProcesses;

    // We can use any syntax that's private to the host (not only 
    // language syntax).  This is not necessarily portable from host to host
    if (SUCCEEDED(spEval->EvaluateExtendedExpression(
        USE_CURRENT_HOST_CONTEXT, 
        L"@$cursession->Processes.Where(p => p.Name == \"notepad.exe\")", 
        nullptr, 
        &spNotepadProcesses, 
        nullptr)))
    {
        // spNotepadProcesses will contain a collection of every process 
        // named (exactly) "notepad.exe".  Such can be iterated with IIterableConcept.
    }
}

Requirements

Requirement Value
Header dbgmodel.h

See also

IDebugHostEvaluator interface