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Let’s review the solution to our error and how to use the Visual Studio debugger to validate our work.
Follow Along
To follow along commiting your changes to this course, you'll need to fork the aspnet-comic-book-gallery repo. Then you can clone, commit, and push your changes to your fork like this:
git clone <your-fork>
cd aspnet-comic-book-gallery
git checkout tags/v4.7 -b updating-the-controller
Additional Learning
See these MSDN pages for more information on how to use the Visual Studio debugger.
Keyboard Shortcuts
-
F11- Step Into -
F10- Step Over -
SHIFT+F11- Step Out
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Were you able to resolve the issue?
0:00
Let's walk through the solution now.
0:02
So it turns out we're
making a simple mistake.
0:04
We aren't setting the Id
property on our model instances.
0:08
To fix the problem let's set
the Id property values to 1,2, and
0:12
3 respectively for our model instances.
0:17
Restart the website and
browse to /ComicBooks/ Detail/1.
0:23
Okay, we're at our break point again
just inside the detail action method.
0:30
Just like last time, we could use F10 and
0:35
F11 to step through our code until we
get to the get comic book methods for
0:38
each loop or we could set another
breakpoint on that line of code.
0:43
To save us a little time,
let's set another breakpoint.
0:48
Switch to the comic book repository class
and set a breakpoint on the line of code
0:51
that contains the if statement
inside of the for each loop.
0:56
Now we can press F5 to continue
execution up to that breakpoint.
0:59
This time in the Autos window, we can see
that the comicBook Id property value is 1.
1:05
Press F10 twice to step down to the comic
book to return variable assignment.
1:10
Press F10 again to move
to the break statement,
1:17
which will break us out of the loop
when we press F10 one more time.
1:20
Isn't it cool to see the benefits
of short circuiting the loop
1:24
as we step through the code?
1:28
Press Shift+F11 to step out of the method
and return to the detail method,
1:30
then press F10 to step down
to the return statement.
1:35
Now we can see that the comicBook
variable is set to our first comic book,
1:39
The Amazing Spider-Man #700.
1:43
Press F5 to resume execution, and
here's our comic book detail page.
1:46
While we're here, let's go ahead and
browse to the other two comic books.
1:52
Just change the 1 in the URL to 2 and
press Enter.
1:56
We're at our breakpoint again.
2:01
Press F5 to continue execution
to our second break point.
2:03
We can see that the id argument value is 2
and the comicBook.Id property value is 1.
2:07
That should cause our if
statement to evaluate to false.
2:14
Press F10 to step to the next statement.
2:17
Sure enough the if statement
evaluated to false as we expected.
2:20
Press F5 to continue to
our breakpoint again.
2:25
Now our comicBook.Id property value is 2,
which matches our ID argument value.
2:27
Press F10 twice to see execution
fall into the if statement.
2:34
We found the comic book
that we're looking for.
2:39
Press F5 to continue execution.
2:41
And here's the comic book detail
page showing the information for
2:45
the Amazing Spider Man number 657.
2:49
Now change the 2 in the URL to 3 and
press Enter.
2:52
We're at our first breakpoint again.
2:57
This time let's disable all of our
breakpoints before we continue execution.
2:59
Click on the Breakpoints tab here at
the bottom to show the Breakpoints window.
3:04
Then click on the check boxes here and
here to disable our breakpoints.
3:08
Notice how the little red
circles are no longer filled in.
3:14
That's how Visual Studio officially
indicates that a breakpoint is disabled.
3:18
Press F5 to continue execution.
3:22
And here's our third comic book.
3:26
Let's close Chrome and stop our website.
3:28
If you're using GitHub,
let's commit our changes.
3:32
Enter a commit message of Updated comic
books controller to use repository.
3:35
And click the Commit All button.
3:44
Let's also sync with the remote server.
3:46
Navigate to the synchronization panel and
click the push link.
3:49
>> The Visual Studio debugger
offers a great set of tools for
3:55
debugging errors and helping you
get more familiar with your code.
3:58
Experienced developers often don't
consider a coding task completed until
4:03
they've stepped through their code line
by line, validating its runtime behavior.
4:08
As we were debugging you probably noticed
that we did a lot of switching back and
4:14
forth between Visual Studio and
our browser.
4:19
It's not uncommon for
4:22
developers to have at least two monitors,
which allows Visual Studio and
4:23
the browser to be displayed at
the same time, one on each monitor.
4:28
We're just scratching the surface of
what can be done with the debugger.
4:33
See the teachers notes for
links to additional resources.
4:36
Let's do a quick review of the section.
4:40
We improved the structure of our [SOUND]
comic book data by adding our first data
4:42
models.
4:47
We learned how [SOUND] strongly typed
views can be used to eliminate any
4:47
reliance on the view bag property.
4:52
[SOUND] We applied software design
principles and the [SOUND] repository
4:54
design pattern to improve the overall
code quality of our website.
4:59
And we saw how to use the Visual Studio
debugger to troubleshoot an error.
5:03
We've been busy,
great job sticking with it.
5:10
In the next section, we'll work on adding
a comic book's list page to our website.
5:13
I'm looking forward to
finally having a homepage.
5:18
See you then.
5:22
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