(4) Building great apps by taking advantage of the Visual Studio Debugger and Emulators

hi and welcome back my name is Dante
Gagne and I'm going to be continuing the
connect learn series on the universal
Windows platform application development
in this video I'm working with an
application it's a little bit more
sophisticated because I want to show you
how the debugger works inside Visual
Studio to just give you a brief look and
how you can diagnose problems that are
happening in your application we're also
going to learn how to deploy our
application different targets so we can
use the emulators that are built in the
visual studio as well as your external
devices so you can see exactly how your
application is going to work let's go
ahead and jump into Visual Studio at
this point up till now we've been
deploying only on the local machine this
combo box up here at the top allows me
to choose what device I want to deploy
to now the default is local machine
assuming you're working on a Windows 10
machine and you're deploying to an x86
architecture now if you're working on an
x64 or an ARM architecture it's probably
switched over here to device meaning
that you can't actually deploy those to
your local machine the defaults are ones
that you're going to be able to work
with so it's not an issue I can go down
here and choose device if I have a
secondary device that I can connect to
and deploy my application to it so if I
want to see exactly how it's gonna work
on a particular phone that I want to
hold in my hand the way a customer would
I can use a device entry in the
drop-down alternatively I can go down to
the mobile emulators which when I select
one of those it'll launch the emulator
that comes with the Visual Studio
Universal windows tools and it will go
ahead and side load my application onto
that I'm going to go ahead and select
one of the emulators and press play it
takes a moment or two once I press play
because it's going to compile my
application it's going to launch a
mobile phone load the operating system
onto it and then deploy my device over
to it so it's actually a couple steps
but if you're just patient with me here
for a moment there's the running
application now I'm just gonna close the
mobile emulator because I want to show
you that it worked but the kind of
debugging that we're gonna do here we
can do just as easily on the local
target so let me switch that comma box
back up here to the local device and I'm
gonna go ahead and press play now I
happen to already have a breakpoint set
and let me explain exactly what those
are now if you've worked with two
buggers before you're probably already
familiar with breakpoints but just in
case you're not let me go over the
basics
while my application is running if I set
a breakpoint somewhere in the code as
soon as the line that the breakpoint is
on is evaluated just before evaluation
it will pause my application and switch
control over to visual studio now I've
already got one created here so as soon
as I click this you'll see the visual
studio is hit this break point for me in
this case it's telling me hey I'm about
to evaluate this command adding or
removing a breakpoint is as simple as
clicking over here over in the left
margin and if you notice as soon as I go
over a breakpoint there's even a cog up
here that allows me to modify how the
breakpoint is going to behave so for
instance maybe I want the breakpoint to
only trigger if I've hit it a hundred
times or maybe I don't want to stop
execution
I just want to output to the debug
window hey we just did this you can do
all that through the breakpoints
settings for these purposes I just need
a basic breakpoint so I'm gonna close
this window and now I've got complete
control over my application I can put
the mouse over any variable and you can
see over in the window it's telling me
hey my category name at this point is
appetizers you can use these to figure
things out like are you getting
unexpected input are you eating values
that you shouldn't beginning these
commands up here allow me to control
where execution is going to go next step
into is the most common this one allows
me to follow the execution chain into a
given method once I'm inside I can press
step over because well let's say I know
what that method does I'm not interested
I can just step over and not have to go
through execution of each individual
command I can also set another
breakpoint later and just hit the
continue button and it will evaluate all
of the commands up to that point these
are very basic debugging commands but
you'll find very quickly that when
you've got an error if there's nothing
better to help you figure out what's
going wrong the last button step out of
will simply finish execution of the
method that you
in and return to wherever you were when
you stepped into so basically once you
step into a method oh wait I already
know what this does you press step out
it'll return execution wherever you
previously were once you've finished
getting the information you need you can
just hit continue and as long as no
other breakpoints are hit execution
returns back to your running application
the breakpoints in the debugger are a
great tool to help you find out when an
application is doing something you don't
expect get in there and diagnose what
the issue actually is the debugger is
absolutely invaluable for figuring out
what's going wrong in your application
but in the next video I'm gonna take the
next step and show you how to debug the
more difficult issues like performance
I'll see you then
you