This interface represents a context for expression evaluation
A call to IDebugStackFrame2::GetExpressionContext returns the this interface. This interface is accessible only when the program being debugged has been paused and a stack frame is available.
An evaluation context can be thought of as a scope for performing expression evaluation.
When a program has halted, the session debug manager (SDM) obtains a stack frame from the DE with a call to IDebugThread2::EnumFrameInfo. The SDM then calls IDebugStackFrame2::GetExpressionContext to get the IDebugExpressionContext2 interface. This is followed by a call to IDebugExpressionContext2::ParseText to create an IDebugExpression2 interface, which represents the parsed expression ready to be evaluated.