Part 12 - C# Tutorial - switch statement in c# continued Video Lecture

hello welcome to prism technologies i'm
venket this is part well switch
statement continued in bar 10 we have
seen if statement in part 11 we've seen
the introduction switch statement in
this part we will write a sample coffee
purchasing program using switch guru and
break statements so let's get to the
demo now I want to write a very simple
program which enables people to buy
coffee and ultimately present a bill so
first let's present a menu to the user
console dot write line and L coffee shop
sells three sizes of coffee coffees more
one for small to maybe two for medium
and three for large okay so once the
user has made a choice he will enter his
choice on the console in a one two or
three we need to read that from the
console and let's do that in a variable
let's call that variable user choice
so console dot read line reads the
number in the form of a string so we
need to convert that to integer and we
do that using the parse method so once
we have converted that to integer now we
need to decide ok in our coffee shop the
small coffee cost is you know maybe one
dollar medium coffee two dollars and
large coffee three dollars so we have to
calculate the cost accordingly so to
store the cost of the coffee let's
create a variable and maybe we'll call
this total coffee cost
and we'll initialize that to zero so we
will switch on the users choice
so if users choice is case one in the
sense he has selected a small coffee
small coffee costs in a one dollar so we
can say total coffee cost total coffee
cost plus equals one okay we're also on
the other hand if the user has purchased
a medium or a large coffee if it's
medium then the cost of the coffee the
cost of the coffee is 2 if it is large
then the cost of the coffee is three
dollars all right if the user has
selected any other option apart from one
two or three we want to present an error
message on the screen saying that his
choices invalid so on a default console
dot write line whatever his choice was
so your choice is invalid and his choice
is present in that users choice variable
so we print that and then we break out
of this loop so look at this until now
we have written a very simple program
all we are doing is present a menu to
the user and the user will select one of
the options and once he enters his
choice you know if it's one you're
calculating it is $1 $2 $3 respectively
if it's not any of those choices from
the menu then we present a message
saying that invalid user choice
so let's go ahead and run this at this
point okay it's asking the user to enter
his choice there so if I enter - so
press any key to continue it's not doing
anything
we are just calculating the total cost
but we are not printing the message so
let's go ahead and do that so finally
when he is done with his coffee shopping
so console dot write line thank you for
shopping with us and we need to present
the bill amount so console.writeline and
whatever is the bill amount bill amount
equals to - coffee cost so we are
printing the total coffee cost now if we
go ahead and run that okay so we have to
choose from those options let's say I
went to a large coffee
I entered three so thank you for
shopping with us bill amount equals
three now let's make this program a
little more interactive by allowing the
user to buy an hour to shop as long as
he wants because right now if he wants
to buy another coffee he has to run the
program again rather than doing that
let's put this program and some kind of
a loop using guru statement so that he
can continue shopping you know as many
coffees as he wants until he decides
okay don't buy any coffee then we will
terminate the program let's see how to
do that instead of running this every
time he wants to buy a coffee so we want
to present the bill at the last after he
finishes shopping so even before that we
will ask the user console.writeline
do you want to buy another coffee
and the options for these are yes are
now okay so the user now will enter a
cirno so we have to read his choice from
the console and stool that and a string
variable user choice okay we already
have the variable called user choice
we'll use user decision maybe use the
decision whether he wants to buy another
coffee or not so we can use another
switch statement or if-else it's up to
you but let's use switch statement
because we're learning about that right
now
so switch on user decision okay now
there's an important thing to note here
now look at this here in the first
switch statement the data type is
actually interior so if the user choice
is one one as an integer two is an
integer three is an integer and we have
student that in this variable of type
integer so we have the case is actually
an integer because we are switching on
an integer data type your case has to
respect that so if it's an integer here
that you're switching on it has to be
integer on every case except for the
default similarly here the user decision
variable is carrying a string datatype
okay so now when you switch you know
you're switching on a string datatype so
your case has to match that data type
and strings are usually within double
quotes so if yes he wants to continue
shopping so if he wants to continue
shopping we want to present the menu to
him once again so we want the control to
go here so we create a label and what's
the label will just come to that in just
a while it's kind of a marker okay so
I'm creating a label called start now
what do you
we'll talk about labels in just a minute
so if the user wants to buy you know
another coffee we have to go to start so
what we are saying is okay he wants to
buy another coffee so the control will
immediately go to start and then it
again presents a menu to the user and as
usual the process goes on until it comes
back here again
okay so what's a label a label is a kind
of a marker in a program you know where
you you're good to can jump ok if this
label is not here I don't know to tell
my program how to go to this
disconsolate right line and I'll go
there and start executing that again so
that's why we can mark our code with
labels so this position in this program
is called a start and if the user
decides to buy another coffee
I want the control to jam to this
location and start executing the code
from there again so a label is a marker
in the code to identify a location where
you want the control to jump back so on
the other hand if the case is no if the
user has decided ok I have done enough
shopping I don't want I don't want to
buy any more coffee then he can just
quit so what we do here we don't do
anything just break out of the case
statement there and if it is a default
he didn't enter yes or no
he entered something else so at this
point of time we want to present him
with an error message that his choice
isn't valid so what do we do
console.writeline your choice
is invalid your choice is invalid please
try again okay
and then it has to go back to this
location here okay because we asked him
to enter SL now but he entered some
garbage which the program cannot
recognize okay so we need to ask him
okay
the options are very clear it has to be
yes or no nothing nothing else okay so
we need to tell the program to go there
and start executing that piece of code
again and to do that you need a second
marker there so let's say we call this
as decide location
okay the user has to decide whether he
wants to buy the coffee or not so what
we can do here is go to the side okay so
it goes here and again it asks the user
that he wants to you know continue
purchasing another coffee or not another
important thing to notice here is that
every case statement usually if you look
on the top every case statement has a
break statement
meaning this case is true execute this
piece of gold and break out of the
switch statement okay but here in this
switch statement may either have break
or go to so we don't have to use break
if I use go to because look at this the
moment I hover my mouse away there is a
green squiggly there a green squiggly in
C sharp indicates it's a warning it's
not an error okay and if you look at the
intellisense it says unreachable who
detected that means this piece of code
is never going to get executed because
why if this condition is met if the user
decision is yes we are saying go to
start so what happens the control
immediately jumps back to the start
label at the top of our program and
starts executing there so this code will
never get executed so there is no need
to have the break statement it already
is getting out of the switch statement
when it encounters this guru so there is
no need to include break statement if
you have a go-to statement there all
right so let's go ahead and run the
replication and see if it works fine
without issues so it's asking the user
to choose let's say I want to buy a
large coffee do you want to buy another
coffee I would say no maybe carbage your
choice okay so there is a problem our
program we haven't and I'll substitute
the value for that placeholder so let's
fix that so your choice we need to enter
that their user decision whatever he has
typed so let's go ahead and run this
okay so let's say I want to buy a medium
coffee this time so do you want to buy
another coffee I say garbage your choice
whatever it is invalid please try again
so it's working as expected let's say I
want to buy another coffee yes okay
let's say I want to buy another medium
coffee now it's asking me do you want to
buy another coffee let's say I enter all
capital letters
look at that I'd say yes but I'm I'm
entering all capital letters let's say
see again your programs is your choice
yes it's invalid yes this yes let it
smaller capital letters my program is
not kind of treating that yes as yes
because the case doesn't match so let's
make a program you know consider all
forms of s whether it is small or
capital or a mix of capital and small
letters how do we do that once we get
the user decision okay however he enters
that you know small letters capital
letters a mix of them okay we will base
our decision on a consistent scheme so
these labels case labels yes/no they're
all capital letters so whatever the user
enters I'm going to convert that to an
uppercase using this function okay on
the string I'm calling a function called
to upper which will convert
all the characters in that string to an
uppercase so now no matter what the user
types you know it will all be uppercase
and if it is yes word it matches yes if
it's no good at matches now otherwise it
gets into the default we will talk about
string manipulation functions in a later
module in a very great detail and they
actually cover functions in this module
so let's go ahead and run this so one
for small two for medium three for large
let's say I enter some 234 which is not
a valid menu your choice 234 is invalid
do you want to buy another coffee now
this is problematic now it's it's a I
mean my choice is invalid so it should
go back and say okay your choice 234 is
invalid so you you have to choose one
two or three
so my first switch statement is not
working as expected so let's go and fix
that so if it is default instead of
going to this one do you want to buy
another coffee because I haven't made a
purchase yet okay so what I can do
instead of breaking here I can just say
go to start meaning my choice is an
invalid choice so I didn't end up buying
a coffee so go back to the start
location and execute again okay and just
to make this program select your coffee
so please select your coffee size let's
say I enter 234 now your choice 234 is
invalid please select your coffee size
so let's say I want to buy a large
coffee we want to buy another coffee
let's say I enter a max of small and
capital letters say yes
please select your coffee size let's say
I want to buy another large coffee look
at this now
I respect you of whatever I have entered
mix of small and capital letters it's
still working and are all small letters
it still works so let's say another
large coffee so until now I have
purchased three large coffees so if the
program is working as expected a large
coffee cost three dollars three into
three dollars is mine nine dollars is my
total bill at this point I want to
conclude my shopping so I will type No
thank you for shopping with us bill
amount is nine dollars plus any key to
continue and I do that the program
terminates so it's a very simple program
basically you know multiple up to switch
statements that we are using okay so
that's it for today thank you for
listening and just before we wind up
let's go ahead and conclude so break
statement so if break statement is used
inside a switch statement the control
will leave the switch statement that's
what we have seen and go-to statement
you can either jump to another case
statement or to a specified label so
using go-to you can actually jump to
another case statement for example let's
say I want to go to case one from here I
can actually do that I can say go to
case one and it works without any fine
without a problem let's say I build this
you
you
okay go to case one case is more letter
so if I build s in the status bar you
can see that build succeeded
so using guru you can jump to a label or
you can jump to another case statement
okay
but using route with a very bad
programming style we should avoid go-to
by all means this because if the control
jumps randomly from one location to
another location debugging of that
program will become extremely complex
and anything that you can achieve with
the go-to statement can be achieved with
loops later in and loops module we will
rewrite this same program using a while
and do-while loop okay and we can by all
means if there is a possibility to avoid
goto statements please do so because it
makes programs more complex to debug
thank you for listening have a great day