Part 17 - C# Tutorial - Method parameters.avi Video Lecture | C sharp: Enhance your Skills (English) - Back-End Programming

so welcome to prism technologies I am
venket this is part 17 different types
of method parameters in c-sharp in part
16 we had a basic introduction to
methods where we have seen the basic
structure from the third the capability
of passing parameters and the capability
of returning values back from a method a
method M c-sharp can have full types of
different parameters value parameters
reference parameters output and
parameter arrays in this session we will
also discuss in on the terms method
parameters and method arguments let's
look at an example okay let's say I have
a very simple method public static and
the method is not written anything back
so worried and let's call this simple
method and this method is going to take
a parameter let's say int J and all this
method does is if we pass it an integer
it's going to change the value to 1 0 1
that's it
whatever value that you pass in to this
method whatever integer that you pass in
to this method this method is going to
change that value to 1 0 1 that's about
it it's not going to do anything else
apart from that ok now to call this
method since it's a static method we can
just refer to that method by name in the
previous session we have seen to invoke
static method you can just use the name
of the class you don't need to create an
instance of the class since we are in
the same class you don't even have to
specify the name of the class so you can
either call it like program dot simple
simple method or simply simple method
okay so we need to pass it a parameter
so to do that let's create end I is
equal to zero I have a variable of type
integer which is initialized to zero and
I'm passing i dot variable as a
parameter I'm passing I as a parameter
to this method now consume the right
line we want to see what the value of I
is look at this here we have this
variable I which is initialized to zero
and we are passing that variable as a
parameter to this method now what will
this method do it will receive that
value into this variable called J and
then it's changing that value to 1 0 1
so now will that change the value
carried by I is initially 0 you pass in
0 to this method this method when you
pass a parameter like this you are
actually passing a value that is
contained in this variable so this
method will make a copy of that value
which is 0 in this case and then it does
whatever processing it has to do in this
case the method is changing the value 0
to 1 0 1 so J so if you look at in the
memory the setup will be like this if
you pass by value so I was 0 ok now I
was 0 ok so I is 0 now you're passing I
to the simple method so what's going to
happen this I is copied into this
variable so you have I 0 and J is also 0
by the time you pass it there and then
in this method you know this method is
changing the value of J 2 1 0 1 so J
becomes 1 0 1 but I still remains 0 so
if we print out the value of I now it
should print 0 and not 1 0 1 because we
are passing the
parameter by value so a value is passed
into this method and it changes that
value so only the variable that is
pointing to this one gets affected but
not the initial variable but on the
other hand let's make a simple
modification to this I am using the
keyword called RAF on this parameter
meaning this parameter is no longer a
value parameter it is now turned into a
reference parameter okay
so when you call the method you have to
use the left keyboard as well okay so
now what is going to happen in memory it
will not create now the runtime will not
create two different variables okay I
mean there are two different variables
but they point to the same location in
the memory so fast it creates a variable
I initialize that to zero so what
happens I and in the memory location it
is zero I is pointing to zero now since
we are passing I by reference to this
method
what's going to happen this value is
zero here but then but since we are
passing by reference this method will
create another variable called J but
that will point to the same memory
location okay so I and J are basically
pointing to the same memory location
right now
now if J changes okay at the moment
would I and J are pointing to zero now
in our method J is changing the value
that is presented this memory location
from 0 to 1 0 1 and I is also pointing
the same memory location so if we go
ahead and print the value now it should
be 1 0 1 instead of 0 ok so that's the
basic difference between passing a
parameter by value and passing a
parameter by reference so if you are
passing by value I and J are pointing to
different memory locations there are
different copies so operations on one
variable will not affect the value
contained
by another variable okay but whereas if
you pass by reference inj or pointing to
the same memory location though they are
different variables they are pointing to
the same memory locations so obviously
operations on one variable will affect
the value contained by the other
variable that's why in our program in
our dough is initialized to zero since J
is changing that value to one zero one
and in this example I and J are pointing
to the same memory location so I values
also one zero one okay so that's passing
by value and passing by reference all
right the next parameter type that we
will look at is an output parameter okay
now when do we use an output parameter
before we answer that question let's
write a simple method let's get rid of
all these okay I want to write a simple
function which can add two numbers and
written their sum so how do I do that
since I want the sum to be written and
found as an integer datatype I will have
intestine type for my method
and let's make the static as well public
static end and let's say we will call
this method s calculate end first number
and second number so all I want this
method to do is let's say return first
number plus second number so if you look
at this method this this method is very
simple okay all it's doing is it expects
two parameters to be passed in summing
up those two entertaining then back now
if I have to read in just the sum that's
fine but let's say I want you to write a
method which can return back both sum
and product how do we do that okay since
a method can have only one written type
we can only return one value okay so
it's not possible to written more than
one value so obviously whenever you want
written more than one value from a
function that's when you can make use of
parameters so let's see how to make use
of output parameters and written both
sum and product it's very easy to do
okay these two are the parameters you
know the first and second number and now
I need to have out end sum and another
variable to hold product out and product
so what's going to happen now is we will
add these two numbers and put the sum in
this parameter we will multiply these
two numbers and put the product in this
parameter so let's see so since we are
using output parameters we don't need
this written type anymore because we
will put the sum into the output
parameter so sum equals first number
plus second number so now this parameter
contains the sum of these two numbers
similarly
that equals first number into second
number so now this parameter contains
the product of these two numbers so now
we can call this wherever we want so if
I have to call this method calculate and
let's say I want to add 10 and 20 and
multiply them as well now look at this
okay these are the two numbers I want to
be added and multiplied okay now when
they are added we know that the sum will
be stored in a third parameter and the
product will be stored in the fourth
output parameter so we need two
variables to receive those values so
before we call that let's create those
variables let's say end may be to tow
equal to zero and maybe end product
equals zero so now what we can do we can
actually pass those and total and out
for that okay so you know when you
create output parameters you use the out
keyword not only in the method
declaration but also in a place where
you invoke the method you have to use
the out keyword okay and so if we want
to print the sum and product
respectively we can say console dot
readline sum equals placeholder and
product equals another placeholder so
sum is present in our total variable and
the product is present in our product
variable so if we go ahead and run that
it should show the sum as 30 and for a
test 200 10 into 20 all right so that's
about output parameters so if you want
your method written more than one value
then output parameters is a solution and
the last type of parameter that we look
at is parameter race
let's look at an example okay basically
parameter arrays you know we have seen
value parameters reference parameters
output parameters parameters arrays are
usually decorated with params keyword I
mean we use params keyword okay to
create parameter arrays
let's look at an example let's say I
have a method public static void
Graham's method that's what will give
the name okay now if we wanted to create
value
you know output parameters we use the
out keyword reference parameters we use
the ref keyword if we want to create
parameter arrays we use params keyword
so params and let's say I want to create
an integer array and I'm passing numbers
okay parameter is so now let's say I
want this method to find out the total
number of elements in this collection in
this array and print those okay so if I
want to find out the total number of
elements in the array controller trade
line numbers dot length property will
give us the number of elements okay and
maybe we want to just say there are
elements okay and this placeholder will
be replaced with this and we want to
print those elements as well so we can
make use of the for each loop for agent
I n numbers
okay so this is a very simple method all
this method does is it takes in an array
as a parameter and then whatever array
that you pass in it will find out the
number of elements in the array and
print those that's what this method does
since we have used the params keyword
here okay actually let's see if I don't
use the params keyword it's like a value
parameter and now when I invoke this
method let's create an array first
integer array let's say numbers equals
new end of let's say three and let's
initialize this array in numbers of 0
that is equal to 1 0 1 similarly let's
populate the rest of the elements 1 0 3
this is 1 this is 2 ok so now we have
this array now if I call this method
params method now look at this this
method is expecting an integer array to
be passed in if I don't pass an integer
array look at what's going to happen a
red squiggly indicates an error no
overload for method params
takes zero arguments we will talk about
method overloading in a different
session but what we need to understand
here is that this method is actually
expecting an integer array to be passed
but we are not doing that that's why we
get a compiler error okay but if you
want to make that pattern that parameter
optional then we can make use of params
keyword so if I use params keyword
keyword then if I use params keyword
then even if I don't pass the array to
it you know it's expecting an integer
array even if I don't pass an array it's
not a problem so if you want to make
your parameters optional one of the days
to use parameter arrays if I go ahead
and run this
you know since there are no elements in
this array what does it do there are
zero elements and there's nothing to
print so obviously there's nothing and
obviously another way to call this is to
pass your array so if I pass this array
let's comment this line and by the way
to comment you can use these buttons
with top so v run this look at this this
array we have three elements one z11 z22
and those are printed okay that's
another way of calling it actually the
greatest benefit of using parameters a
parameter arrays is that you can also
invoke this method just by passing you
know the numbers separated by comma you
can pass as many as you want for example
let's say 1 comma 2 comma 3 comma 4
comma 5 okay
so there's really no theoretical
limitation on how many you can pass
since this is an integer array you can
pass as many numbers as you want
separated by comma this is another
flexibility that we have when we make
use of parameter arrays so if I go in
and run that there are five elements and
those are the five elements okay but one
thing to keep in mind when using
parameter arrays is that this has to be
the last I mean in case if you if your
method is going to have multiple
parameters the parameters are a should
be the last one in the parameter list
for example if I want another pair if I
want to pass another parameter into X ok
this is fine but what is not fine it's
this one you cannot have you know the
other parameters in the end you know
params array has to be the last one in
the list of the parameters for that
method okay and you can only have one
parameter as a parameter array you
cannot have another parameter array
maybe of string type
and names you can't do this you will
still get an error okay so that's about
parameter arrays so the parameter would
basically lets us specify a method
parameter you know that takes a variable
number of arguments you can send a
comma-separated list of arguments as we
have seen or an array or no arguments at
all params keyword should be the last
one in a method declaration and only one
graham's keyword is permitted in a
method declaration okay we'll also
quickly understand the difference
between method parameters versus method
arguments because this term is very
commonly used and if you're new to
programming you know when you read some
articles you might be confused okay one
what is method parameter and what is
method argument okay whenever we declare
a method okay here when we list our
parameters you know these are called as
parameters in the method declaration but
the but when we actually invoke that we
pass values for these parameters so that
this array we are passing these values
so these are this is called as an
argument an argument for this parameter
okay so in method declaration we call it
as method parameter but then we invoke
that and when we pass values those
values are called as arguments for those
parameters so that it will be helpful
for you when you read articles online
okay so we have seen this passing by
value and passing by reference so
obviously in this session we have seen
different types of parameters in the
third can have there are four different
types of parameters C sharp value
parameters reference parameters output
parameters and parameter arrays we also
have seen the difference between method
parameters and method arguments that's
it for today thank you for listening
have a great day