Debugging means poking around, usually at a point in the execution. You set a breakpoint, fire up the debugger, and start pokin'.
Sometimes "poking" means "typing in expressions and seeing the result values." This is where Evaluate Expression helps. It is a popup window where you can type in values and see the results, in the scope of the stopped line: all the values in that block, passed in, etc.
There are several ways to get to the popup:
Click the debug toolbar button to launch it
Evaluate Expressionaction (
Right-click in the editor and choose
Note that, if you have a selection in the editor, that selection is
filled into the
Evaluate Expression input box. This is a very handy
way to stop on a line, then execute part of that line, without retyping
or even cut-and-paste. This also means
Evalute Expression can be
driven with the keyboard instead of the mouse.
As you are typing in the
Evaluate Expression input box, autocomplete
and other features are available. Also, previous expressions you've
typed are available as autocomplete and in the dropdown.
If you type something in that causes a new variable to be defined in that
scope, or changes an existing variable, the
Variables pane will reflect
it. Meaning, you are indeed changing the scope.
One last point: if you move around in the stack frames (left panel),
Evaluate Expression will be driven by different scope. Thus if you
want to "poke around" inside some code that called the line at the
breakpoint, it's easy.