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Expression evaluation context

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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

In Visual Studio debugging, an expression evaluation context:

  • Represents a context for expression evaluation. Generally, an evaluation context corresponds to the lexical scope within which to evaluate variables, parameters, functions, and methods. For example, an expression evaluation context associated with a stack frame will provide the context for evaluating local variables, method parameters, and class members (if applicable).

  • Exists when a program has stopped at a breakpoint. The expression itself is a data structure representing a parsed expression that is ready for binding and evaluating within the given context.

    In more detail, expressions are created using the ParseText method. When an expression is evaluated, it generates a printable string containing the name and type of variable or argument and its value. This string is displayed in the Watch window or in the Locals window of the IDE.

    Given a BSTR and an IDebugExpressionContext2 interface, a debug engine (DE) can create an IDebugExpression2 interface by parsing an expression. Given an IDebugExpression2 interface, the DE can get a value through synchronous or asynchronous expression evaluation. This value, along with the name and type of the variable or argument, is sent to the IDE for display.

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