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So let's go into the PowerShell console.

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We'll look at generating some errors and exceptions,

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and then we'll look at how to handle those errors and exceptions.

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One of the downsides of using any kind of programming construct is,

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of course, getting errors in your script that you're running.

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So maybe you execute a common command, and it fails because,

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for example, like we did previously,

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where it was the wrong input value or the wrong type,

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and then an error is thrown, which kind of messes up the code.

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And so one of the most important things about building PowerShell scripts

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is to be able to handle the errors in a graceful way.

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Now, one of the options that we have is obviously to do what's called Throw,

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which is to throw a specific error.

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So what we'll do is we'll just create a kind of

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basic function within PowerShell.

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So let me just do function, and we'll call it New‑Error.

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We'll obviously do kind of brackets here.

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Let's do this.

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And we'll use the word Throw, and then I'll do a message, "This is an error".

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So let's do that.

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And then we'll close that like so.

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Okay, so now we have a function that's available to us,

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so I can say New‑Error, and then instantly when we run it,

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it throws that error.

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And you can see in PowerShell 7 it highlights that for you.

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So it'll come back with an exception error,

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and then it will say, this is the line or the object that through that error.

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So when we're trying to handle things, you could just do this.

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You could say, Throw an Error and literally get rid of it.

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Now, of course,

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that doesn't really help too much when you're trying to build

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something that's a little bit easier to handle and can handle the

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user flow and the user interaction.

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So another option that we've got is to actually use

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something called Write‑Error, which allows me to write an error out.

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So if I just do this, Write‑Error,

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and then it's got a property which is available to us called ‑Message,

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so I'm going to add a message, "This is an error",

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so the same message.

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And then what we get is this kind of error action that's available to us.

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Now before we do that, let me just press Enter here.

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Now, this will literally just right the error message and say,

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"This is an error".

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Nothing spectacular.

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But if we're trying to handle that process,

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then we can also use what's called ‑ErrorAction ID.

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And if I just do this one, we can tab, SilentlyContinue, Stop, Suspend.

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So we can flick between what we would like to do when an error is generated.

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So if I say Write‑Error ‑Message and Stop,

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now, obviously, it's just one line, so it's just going to stop.

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This will cause the PowerShell function,

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method, whatever it is to actually stop working at that point.

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So what does that look like if we tie everything together?

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So let's go back and do our New function again, so New‑Error.

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We'll repeat the same process as before,

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but this time we'll do a little bit of a calculation,

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so kind of using some of the things that we've done previously.

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So for i, so let's do $i is a variable = 1.

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So we're using a for loop here,

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and then we'll say as long as the i is less than or equal to 10,

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so we're going to do a bit of a count here.

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I can then do i and ++.

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Okay, so let's do that first bit.

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What I'm going to do is write a message to the screen,

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so what we've done in the past.

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"The current number is, and then, of course,

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we've got this variable of i that's being populated,

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that we can then render inside this message here,

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so we'll do this.

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And then we'll go down to the next line,

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a nd then what we'll do is we'll throw an error message at this point.

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So we'll say, "This is an Error", like so,

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go underneath it,

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and then we actually want to increment a number tw whatever that would be.

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So add that one again, close it out, and then we can close the function out.

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So we now have our new function.

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So let's just review.

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We have a New‑Error function.

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It starts with the number 0,

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and then it counts from basically 1 to everything that's

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less than 10 by adding a number to it,

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and then what it will do is it will continue to add and write a message,

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and then at some point it's going to throw an error.

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So what we'll do is we actually run it straightaway,

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and, of course, what happens?

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It just says the current number is 1, and then because it threw the error,

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it cannot do anything else.

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So throwing an error will literally cause everything to stop.

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So let's go a little step further,

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and we'll take that same function that we just built.

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So let me just loop through my commands a little bit here.

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So there's my clear command, New‑Error.

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Not the Write‑Host.

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Let's go number, function.

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There we go.

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Function number is 0.

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We'll go back to the for loop.

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We'll then do the same command as before for the Write‑Host.

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Now this time we're not going to throw an error.

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We're going to say Write‑Error instead, so exactly the same thing.

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We'll do the message that we're going to enter,

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so we'll say, Write‑Error ‑Message.

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And so we want to represent the fact that an error was caused.

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And I'll say "Error", just like so, to keep it short and sweet.

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But then what I'm going to do is do an ‑ErrorAction.

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Oops, ‑ErrorAction, like so, and I'm going to say SilentlyContinue.

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Do Enter.

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And then, of course, I need to add my next line,

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which is, if I just go back here, function.

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I'll tell you what.

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We'll just write that one out, which will be $number += $i,

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and then we'll close and close.

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So, now I have my function updated.

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So before we call it, let's just double check.

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Same thing again.

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Start with a 0, iterate from 1 to 10, checking that it's less than 10.

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It will write a message saying the current number is something.

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Then it will write an error, but this time it should silently continue.

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So let's just press Enter.

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And sure enough, it does.

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Now notice it didn't render anything.

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It just silently continued and finished all the way to number 10.

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So we captured the error.

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We effectively grabbed it, and we could have done something.

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I chose to write an error, but of course, I told it to silently continue also.

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So if we go back and if we go looping through it pretty quickly here,

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function, number, for loop, Write‑Host, and change it from SilentlyContinue to,

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let's do Suspend, and then let me get rid of this here.

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I have to obviously do my $number += $i.

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And then we'll close that one down,

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and then we'll close the next line down as well.

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And so that should then give us our new function, ready to call again.

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And this time around we're telling it to cause a suspension of the code,

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so I'm going to say Error.

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Now, of course, note just what happened.

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If you come all the way through here, we can keep scrolling.

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It's moaning about a specific action.

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You can see that it's looping, and it's trying to do something.

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If we look at the message, it says,

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The Suspend ActionPreference is reserved for future use.

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Perfect.

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It's always good to know that when you're trying to use values,

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you need to make sure that just because something is documented,

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you need to make sure that it's actually useful.

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So the effective options here would be to stop or to

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actually just silently continue.

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So if we do that one more time, number, for loop here,

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I'm going to say Stop, and then I'll do my $number += $i,

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that one, that one, and that one, and then do New‑Error,

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you can see it will just get to number 1 and error.

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So it's a simple way of capturing it, a way of trying to handle it,

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just rendering a message or breaking or stopping.

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It's not the most ideal way of doing it,

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but it does allow you to kind of at least when you break and there's an error,

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then, of course, you can capture what that error would be.

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And, of course, whenever you throw the error,

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you can also capture more information about what that message would be.

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So if I say Throw "Error", like so, it will say Exception.

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But if I say $, let's create a variable here and call it Throw "Error",

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like so, now if I do the error,

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you can see it gives me a whole host of information that's associated to

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that and everything around what the error would be.

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So I can say $error., and if I tab through it,

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you can see I get the regular properties that are available.

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But of course, depending on the name of the variable,

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I can also get access to all of the other values too.

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Now, I will give you a hint here.

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Try not to use kind of the same name as maybe some

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of the default values would be, you know,

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especially when you're using things like the word error or something else.

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They are often reserved words, such as PSItem and things like that.

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So you can see I'm just scrolling all the way back through, and

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you'll see it's a whole host of different errors and messages that

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get rendered from various different things.

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So you have the ability to not only throw an error, but to obviously capture the error details.