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There are several techniques to debugging. In this video, we’ll go over a common technique: logging.
One technique we can use, 0:00 the debugger application, is by logging to the Output window. 0:02 This will allow us to get an idea of what's going on our application without 0:05 actually having to stop or pause the execution of the code. 0:09 There are a couple ways we can write to the Output window. 0:12 The first is by calling the method everywhere we want to log. 0:16 A log is simply a list of messages that we can look through at a later 0:19 point to try to figure out what is happening when a program is running. 0:23 Let's write some logs right now. 0:27 To write logs for 0:30 debugging purposes, we can use the Writeline method of the Debug Class. 0:30 It's found in the System.Diagnostic namespace. 0:35 So right here, let's put using System.Diagnostics. 0:39 Let's log the user's menu selection and song name and program .CS. 0:46 Our logs will be visible in what's known as the Output window. 0:50 We'll go into more detail about the output window later in the workshop. 0:54 For now, just know that this is a place where we can find information 0:57 about how our app is running while it's debugging. 1:00 Let's print out the options selected by the user. 1:03 So right down here after we get the option, 1:06 we can write Debug.Writeline and 1:11 I'll use the format strings syntax here and 1:14 say Option selected, And print out the option. 1:19 And down here, we can print out the song name that the user entered. 1:27 So we'll write Debug.Writeline and 1:32 say New song added songName. 1:38 Now let's run the app with the debugger by clicking on the play button here. 1:44 So the app starts up and Visual Studio switches into debug mode. 1:50 You can see that there are a few more windows open. 1:55 You've got the Diagnostic Tools window, that Call Stack, Autos. 1:57 We can close this Diagnostic Tools window. 2:01 And down here, we see a tab for the Output window. 2:04 Let's expanded it a little bit, so we can see what's going on here. 2:09 Now I'll switch back to the consul and let's add a song. 2:13 So here when I selected option 1, you can see our log was printed to the output. 2:19 Now say Learning To Fly, And 2:25 when I hit Enter, we see another log, a new song added Learning To Fly. 2:29 Now if I quit and stop the application, the Debugger also stops running and 2:37 those other windows close, but the Output window is still available here. 2:42 We can see the logs that we wrote while the program was running. 2:48 And here's the option selected 1 and New song added, Learning to Fly. 2:52 Using this methodology works well in the simplest of scenarios, but 2:58 it can lead to issues for your project if you're not careful. 3:02 One problem is that for each spot in the code where we want to log 3:05 the Output window, we've written a new line of code to do so. 3:09 Over time if this code is forgotten and left in the codebase, the application may 3:13 end up littered with calls that you don't necessarily want or need any longer. 3:17 Similar to the first problem is managing the log statements. 3:22 We don't have a central place to manage all of the log statements. 3:26 When you use this technique, just remember to clean up afterwards, so 3:29 you don't leave any unnecessary statements in your code. 3:33 There's another way to lock the output window called tracepoint. 3:36 Tracepoints are break points that have custom actions. 3:40 If you don't know what a breakpoint is don't worry, 3:44 we'll be covering breakpoints in great detail later in the workshop. 3:46 For now, just know that a breakpoint is a marker set on a line of code 3:50 that Visual Studio can take some actions on. 3:54 Let's remove the calls to Debug.WriteLine and replace them with tracepoints. 3:57 We won't be needing this using System.Diagnostics line either. 4:02 To create a tracepoint, we first need to create a breakpoint. 4:08 To create a breakpoint, we'll find the line that is right after where we would 4:12 have put the Debug.WriteLine statement and click on this gray bar on the far left. 4:17 I'm gonna copy this message right here because we'll be using that later. 4:22 And we can delete the Debug.WriteLine. 4:28 To turn the breakpoint into a tracepoint, 4:31 we need to tell the debugger to do something when this breakpoint is hit. 4:33 To add an action to a breakpoint, just right click on it, select Actions. 4:36 Now here we see the Settings Panel for breakpoints, 4:42 make sure that the Actions checkbox is checked. 4:46 And in the text field, we'll paste our message. 4:49 To make this a tracepoint, we want to have this Continue execution checkbox checked, 4:53 otherwise the execution will be paused when it gets to the breakpoint. 4:58 Let's create another tracepoint down here. 5:03 So here where we say New song added, we'll copy that, 5:06 we'll delete this line, And we'll put a tracepoint right here. 5:12 Another way to add a tracepoint is just to right-click on the line where you want 5:19 the tracepoint, go down to Breakpoint and click Insert Tracepoint. 5:23 Now I can paste our message right here. 5:28 You can quickly identify tracepoints in Visual Studio because they have 5:32 a diamond-shaped marker instead of the circle marker of standard breakpoints. 5:36 Now when we run the application, we'll see our output is the same. 5:40 And a huge benefit is that we no longer need to pollute our code with extra 5:44 statements to log some debugging messages. 5:48
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