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160 Microsoft Visual Studio 2010: A Beginner’s Guide
Inspecting Application State
Application state is the value of variables in your code, the current path of execution, or
any other information that tells you what your program is doing. While debugging, it’
s
important to be able to view application state and compare what is really happening to
what you expected to happen. VS gives you various windows for viewing application
state, which you’ll learn about in this section.
NOTE
When inspecting the state of your application, you’ll need to keep the concept of scope
in mind. When a variable is in scope, you will be able to see the variable’s value. Scope
is defined within a block. In C#, the block is defined with curly braces, and VB defines
a block with begin and end statements. A couple examples of scope involve class fields
and local variables. A private class field would be in scope for all the methods of that
class but not in another class. A local variable would be in scope for all statements
of the method it is defined in, but would be out of scope for other methods. Another
scenario is a for loop that defined a variable in its body—the variable would be in
scope for the body of the loop but out of scope outside of the loop body.
Locals and Autos Windows
The Locals and Autos windows show you the variables in your system at the current
breakpoint. Locals gives you a list of all variables that the current statement could access
(also referred to as in scope). The Autos window shows variables from the current and
previous lines. You can open the Locals and Autos windows from the Debug | Windows
menu when your VS debug session is active and paused at a breakpoint. These windows
may have already been placed for you at the bottom left of Visual Studio next to the
Output window if you’ve not rearranged your VS layout.
As shown in Figure 6-8, the Locals window shows all of the variables in scope for
the Main method from Listing 6-1. The Locals window is a coarse-grained view, and the
Figure 6-8 The Locals window