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[MUSIC]

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Hi everyone, this is James.

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In this C# practice session, you'll get
a chance to practice validating input and

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catching exceptions using C#.

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It reinforces what you learned in
stage four of the C# basics course.

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If you find this practice session
too challenging to complete,

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you might need to review that course.

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See the teacher's notes for a link.

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I've attached a workspace to this video.

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Go ahead and open the workspace or
download the project files

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if you want to use an external editor or
an IDE like Visual Studio.

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If you open the program.cs file,

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you'll see that we've
provided you with some code.

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This code prompts the user for

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a number, calculates the square of the
provided number, and displays the result.

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While this is a functional program,

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there are some improvements
that we'd like to make.

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Each improvement is represented
by a TODO code comment.

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To complete this practice session, you'll
read through the TODO code comments and

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complete each one.

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Let's see the completed program in action.

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Remember, to compile a C# file,
we use the mcs command.

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And to run a C# program,
we use the mono command.

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See the teacher's notes if you need
a refresher on either of those commands.

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Okay, the program prompts me for
a number, I'll enter 2,

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then displays the square
of my provided number.

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2 multiplied by itself is equal to 4.

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We can then enter another number or

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type the text quit to terminate
execution of the program.

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Let's clear the console by typing clear,
Enter.

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Then run the program again.

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Notice that if we don't enter a number,
the program will crash.

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Or if we enter a fractional number like
4.5, the program again will crash.

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And to quit the program, we need to type
the text quit in all lowercase characters.

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If we do any variation of that,

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like in all uppercase characters,
the program will crash.

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As you can see, we've got some work to do.

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Let's review each of the TODO
comments in the program.cs file.

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Our first task is to switch
to using continue and

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break to control the flow of
execution through our program.

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That will allow us to get rid of the
keepGoing variable that you see defined

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right here.

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For our next task, we just need to
update this prompt from Enter a number

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to Enter a number between 1 and 1,000.

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For our next task,
we wanna force the user's provided value

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in the entry variable
to lowercase letters.

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That will allow the user to user to
type the text quit however they want.

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For this task,

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we need to add a try/catch statement
to catch FormatException exceptions.

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This will keep the app
from crashing if the user

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enters something that can't
be parsed to a number.

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For this task, we want to allow
the user to enter a fractional value.

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So instead of just whole numbers,
like 1, 2, or 3,

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we want them to be able to enter 2.4,
for instance.

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For the next couple of tasks,
we wanna validate the user's input.

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For the first one, if the user enters
a value less than or equal to 0,

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we wanna display the message,
Please enter a number greater than 0.

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And for the second validation, if the user
enters a value greater than 1,000,

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we wanna display the message, Please enter
a number less than or equal to 1,000.

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And that's it.

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If you get stuck at any point,
see the teacher's notes for hints and

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links to videos that cover what you need
to know in order to complete the session.

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And if you aren't able to fully
complete the program, don't worry,

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I'll show you how I completed
the TODOs in the next video.

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Good luck and we'll see you in just a bit.