IDebugExpressionEvaluator
Applies to: 
Visual Studio 
Visual 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, please see CLR Expression Evaluators and Managed Expression Evaluator Sample.
This interface represents the expression evaluator.
Syntax
IDebugExpressionEvaluator : IUnknown
Notes for Implementers
The expression evaluator must implement this interface.
Notes for Callers
To obtain this interface, instantiate the expression evaluator through the CoCreateInstance method by using the class ID (CLSID) of the evaluator. See the Example.
Methods in Vtable Order
The following table shows the methods of IDebugExpressionEvaluator.
| Method | Description |
|---|---|
| Parse | Converts an expression string to a parsed expression. |
| GetMethodProperty | Gets the local variables, arguments, and other properties of a method. |
| GetMethodLocationProperty | Converts a method location and offset into a memory address. |
| SetLocale | Determines which language to use to create printable results. |
| SetRegistryRoot | Sets the registry root. Used for side-by-side debugging. |
Remarks
In a typical situation, the debug engine (DE) instantiates the expression evaluator (EE) as a result of a call to ParseText. Because the DE knows the language and vendor of the EE it wants to use, the DE gets the EE's CLSID from the registry (the SDK Helpers for Debugging function, GetEEMetric, helps with this retrieval).
After the EE is instantiated, the DE calls Parse to parse the expression and store it in an IDebugParsedExpression object. Later, a call to EvaluateSync evaluates the expression.
Requirements
Header: ee.h
Namespace: Microsoft.VisualStudio.Debugger.Interop
Assembly: Microsoft.VisualStudio.Debugger.Interop.dll
Example
This example shows how to instantiate the expression evaluator given a symbol provider and an address in the source code. This example uses a function, GetEEMetric, from the SDK Helpers for Debugging library, dbgmetric.lib.
IDebugExpressionEvaluator GetExpressionEvaluator(IDebugSymbolProvider pSymbolProvider,
IDebugAddress *pSourceAddress)
{
// This is typically defined globally but is specified here just
// for this example.
static const WCHAR strRegistrationRoot[] = L"Software\\Microsoft\\VisualStudio\\8.0Exp";
IDebugExpressionEvaluator *pEE = NULL;
if (pSymbolProvider != NULL && pSourceAddress != NULL) {
HRESULT hr = S_OK;
GUID languageGuid = { 0 };
GUID vendorGuid = { 0 };
hr = pSymbolProvider->GetLanguage(pSourceAddress,
&languageGuid,
&vendorGuid);
if (SUCCEEDED(hr)) {
CLSID clsidEE = { 0 };
CComPtr<IDebugExpressionEvaluator> spExpressionEvaluator;
// Get the expression evaluator's CLSID from the registry.
::GetEEMetric(languageGuid,
vendorGuid,
metricCLSID,
&clsidEE,
strRegistrationRoot);
if (!IsEqualGUID(clsidEE,GUID_NULL)) {
// Instantiate the expression evaluator.
spExpressionEvaluator.CoCreateInstance(clsidEE);
}
if (spExpressionEvaluator != NULL) {
pEE = spExpressionEvaluator.Detach();
}
}
}
return pEE;
}