Visual Basic Tutorial - 135 - Exit Try And Throw Video Lecture | Mastering Visual Basic - Web Development

hello YouTube sam here from youtube.com
slash on live gamer for the new Boston
and in this tutorial we're gonna be
talking about the exit try statement and
if we have time we'll also be talking
about the throw keyword so what the exit
try statement does is it's basically
like any other exit statement like exit
sub exit four or exit do all of those
will exit the current statement that
it's in so let's say we'll go ahead and
type if index is greater than or equal
to let's say my array dot length and I
think it's minus one so if it's greater
than or equal to my array dot length
minus one what do we want to do we want
to exit the Tri so let's go ahead and
run this and if we did this right it's
going to exit the Tri before it prints
one I'm so many would exit after it
prints one but you still get the idea of
what it does it will just exit the
statement and it will go past this catch
statement right here this it will not
see this and it will go through the line
of code that is right below it so it
goes below the entry and runs whatever
code is right there now exit tri is a
very simple concept just like any other
exit keyword so what we're going to talk
about now is throwing throwing
exceptions so we'll just type if index
is greater than or equal to my array dot
length what do we want to do we want to
throw and you can see here that the
description says throws an exception
within a procedure so that you can
handle it was structured or unstructured
accepts an exception handling code so
this will just throw the exception
before the exception actually happens so
if an exception is about to happen let's
just throw
right here and we'll handle it down here
in the try-catch statement I mean the
catch statement so we want to create a
new exception and we will throw an index
out of range exception and for our
parameters we can add a message so we'll
just say
okay so we're gonna throw a new index
out of range exception and it's gonna
say you retard
don't try to access memory that isn't
there so now we're gonna do is we're
going to catch that exception so we'll
type index out of range exception and
for our code we will just show that in
there so II X dot and what we're gonna
do instead of two string we're gonna get
the message for that so it's going to
show our message that we typed in right
here so let's go ahead and run this you
can see that when we click at all it
says you retard don't try to access
memory that isn't there now the message
will not show up if we just do a X dot
two strings so go ahead and run this and
it's gonna give us the same stuff that
we did last time and it looks like you
did show up says system dot index out of
range exception you retard don't try to
access memory that isn't there so it
gives us the type of exception whatever
message that is thrown with that
exception and then it shows us all the
information about it sorry I thought I
thought that wasn't gonna be there but
it was so if you do to string it's gonna
show you the information and the message
now it's more it's better coding to just
so the message to the user so that they
don't have to see all of that stuff
right there that they most likely will
not understand now sometimes what you
can also do is throw exceptions just to
get yourself out of some code I wouldn't
really recommend this but sometimes it
is a valid way to get out of code so
let's say you're doing an operation and
if something happens in that operation
you want to throw a new exception and
you just catch that exception right here
and just leave that blank and what its
gonna do is gonna exit whatever
operation you're doing right there and
then come down and start at this line of
code now you can also have multiple
except multiple multiple catch
statements when you're throwing new
exceptions
and you can throw exceptions anywhere
you want in your program but just keep
in mind that it's gonna make your
program crash so let's say we'll go
ahead down here and we'll throw new
exception and for the message it will
type hi I am an exception so for this to
actually show up what we're gonna have
to do is right-click on try-catch and
click build so we're gonna need to run
the debug not the debug we're gonna run
the release so if you head over to your
Visual Studio 2010 my project folder
right here so we got libraries documents
Visual Studio 2010 projects here's our
try-catch project if you go to the
project and then you go to bin release
you'll see your program right here go
ahead and open that up and this is the
release form of your program it doesn't
offer any debugging capabilities so if
we go ahead and click at all it says an
unhandled exception has occurred now
this is built into Visual Basic and it
handles exceptions for you so that they
the user can either continue past the
exception or quit and you can see that
the message right here says hi I am an
exception and that's the message that we
sent to it when we threw that exception
so we can just go ahead and click
continue because nothing bad is going to
happen we can go ahead and close out of
this so go ahead practice with the exit
try statement you can also practice
throwing exceptions in your program or
in your try statement and once you're
familiar with that and you're not gonna
forget it go ahead and move on to the
next tutorial