The Challenge

[MUSIC] 0:00 Hi everyone, this is James. 0:04 In this C# practice session, you'll get a chance to practice validating input and 0:06 catching exceptions using C#. 0:11 It reinforces what you learned in stage four of the C# basics course. 0:13 If you find this practice session too challenging to complete, 0:19 you might need to review that course. 0:22 See the teacher's notes for a link. 0:24 I've attached a workspace to this video. 0:26 Go ahead and open the workspace or download the project files 0:28 if you want to use an external editor or an IDE like Visual Studio. 0:33 If you open the program.cs file, 0:37 you'll see that we've provided you with some code. 0:40 This code prompts the user for 0:44 a number, calculates the square of the provided number, and displays the result. 0:46 While this is a functional program, 0:51 there are some improvements that we'd like to make. 0:53 Each improvement is represented by a TODO code comment. 0:56 To complete this practice session, you'll read through the TODO code comments and 1:00 complete each one. 1:04 Let's see the completed program in action. 1:06 Remember, to compile a C# file, we use the mcs command. 1:10 And to run a C# program, we use the mono command. 1:19 See the teacher's notes if you need a refresher on either of those commands. 1:26 Okay, the program prompts me for a number, I'll enter 2, 1:30 then displays the square of my provided number. 1:34 2 multiplied by itself is equal to 4. 1:37 We can then enter another number or 1:41 type the text quit to terminate execution of the program. 1:43 Let's clear the console by typing clear, Enter. 1:47 Then run the program again. 1:51 Notice that if we don't enter a number, the program will crash. 1:54 Or if we enter a fractional number like 4.5, the program again will crash. 2:02 And to quit the program, we need to type the text quit in all lowercase characters. 2:13 If we do any variation of that, 2:18 like in all uppercase characters, the program will crash. 2:20 As you can see, we've got some work to do. 2:25 Let's review each of the TODO comments in the program.cs file. 2:29 Our first task is to switch to using continue and 2:33 break to control the flow of execution through our program. 2:36 That will allow us to get rid of the keepGoing variable that you see defined 2:40 right here. 2:43 For our next task, we just need to update this prompt from Enter a number 2:44 to Enter a number between 1 and 1,000. 2:49 For our next task, we wanna force the user's provided value 2:52 in the entry variable to lowercase letters. 2:55 That will allow the user to user to type the text quit however they want. 2:59 For this task, 3:02 we need to add a try/catch statement to catch FormatException exceptions. 3:03 This will keep the app from crashing if the user 3:08 enters something that can't be parsed to a number. 3:11 For this task, we want to allow the user to enter a fractional value. 3:14 So instead of just whole numbers, like 1, 2, or 3, 3:19 we want them to be able to enter 2.4, for instance. 3:22 For the next couple of tasks, we wanna validate the user's input. 3:26 For the first one, if the user enters a value less than or equal to 0, 3:30 we wanna display the message, Please enter a number greater than 0. 3:34 And for the second validation, if the user enters a value greater than 1,000, 3:39 we wanna display the message, Please enter a number less than or equal to 1,000. 3:43 And that's it. 3:49 If you get stuck at any point, see the teacher's notes for hints and 3:50 links to videos that cover what you need to know in order to complete the session. 3:54 And if you aren't able to fully complete the program, don't worry, 3:58 I'll show you how I completed the TODOs in the next video. 4:02 Good luck and we'll see you in just a bit. 4:06