Part 69 Making method parameters optional by specifying parameter defaults

hello welcome to presume technologies I
am venket this is part 69 of c-sharp
tutorial
in this video we'll discuss making
method parameters optional by specifying
parameter defaults please watch part 67
and 68 before proceeding with this video
in part 67 we discussed using parameter
arrays and in part 68 we discussed
method overloading in this video we'll
discuss making method parameters
optional by specifying parameter
defaults we'll be using the same example
that we use in part 67 and 68 let's flip
to visual studio so here I have this add
numbers function which is going to allow
the user to add two or more numbers okay
in this function at the moment you know
the first and second number parameters
are going to contain the first two
numbers that the end user want to add
and in case if he wants to add more than
two numbers then those numbers will be
passed as part of this third parameter
here now look at what we are doing the
implementation is very straightforward
we have an integer variable here result
which is holding the sum of the first
and second numbers and then look at this
here we are checking if rest of numbers
is not now okay if it's not null this
rest of numbers if it's not now then we
know for sure the end user wants to add
you know more than two numbers okay in
which case we are looping through that
integer array taking each integer out of
the array and adding it to this result
variable finally we are printing the sum
okay pretty straightforward at the
moment if you look at this function all
the three parameters are mandatory now
let's say for example if I want to add
just two numbers you know when I say 10
20 and then if I try to you know build
the solution look at this I already have
it read quickly there you know it says
no overload so method add numbers take
two arguments because the only
overloaded version of higher numbers at
the moment has three parameters and we
need to supply values for all the three
parameters okay now my intention here is
to make this third parameter optional
and that way I want to make it optional
by specifying a default parameter value
and how do we do that all you need to
is is equal to and you can specify
whatever value you want to specify at
the moment I am going to specify a value
of null okay so look at this right now I
that error has gone away now here the
end user wants to add just two numbers
in which case he is not going to supply
the argument for the third parameter so
if we don't supply an argument for the
third parameter then rest of numbers
will be null in which case it wouldn't
go through this for each loop because
this condition will become false okay so
obviously now if I go ahead and run this
as you might expect the sum will be
thirty okay on the other hand if the end
user wants to add you know more than two
numbers then he can pass a value for the
third parameter as well look at that by
default it's now but I want to add you
know two more numbers maybe thirty and
forty so I am creating a new integer
array and then passing those values
thirty and forty and obviously if I run
this now we should get the sum of those
four numbers okay so in this video we
have discussed how to make method
parameters optional by specifying
parameters parameter defaults but then
one thing to keep in mind is that the
optional parameters must appear after
all the required parameters so here the
first number and second number are
mandatory and required parameters
meaning you have to supply values for
these parameters okay but then the third
parameter is the optional here now the
optional parameters must appear after
all the required parameters now what
will happen if I specify this as the
second parameter let's look at that look
at this if I try to build as let's
comment this method call right there and
let's try to build this and see what's
going to happen so right click on the
project bill look at that it says bid
you fail and look at the error message
optional parameters must appear after
all required parameters okay all right
another thing that we will discuss here
is named parameters now let me actually
to speed things up I have
this method already implemented so let
me copy that and let's flip to visual
studio now if you look at this function
here you know the test function it has
got three parameters here and with out
of these three parameters a is mandatory
it's a required parameter and then B and
C your optional because we have default
specified there and all this function
does is it prints out the values of
whatever we pass in a is equal to a B
and C okay now look at this let me
invoke this function okay so test and
then I'm going to pass a value of one
and two okay
look at that I can just invoke this
function by passing just one because B
has a default value of 10 C has a
default value of 20 now let me run this
so a will be 1 B will be 10 and C will
be 20 okay now let's say I want to pass
the second parameter as well the
argument for the second parameter let's
say I want to pass two now my intention
here is to actually pass this argument
to you know as the value for the third
parameter now let me actually run this
so by default what's going to happen one
will be treated as the argument for
parameter a 2 will be treated as the
argument for parameter B but my
intention is I want to pass to two
parameter C and I want to do a and I
don't want to supply any argument for B
I wanted to use its default is it
possible absolutely that's where named
parameters come into play so now I want
this number to to be treated as an
argument for parameters say so how do i
specify that that's my intention i can
use named parameters look at this the
moment i press in a comma after the
first parameter you know look at the
intelligence it's asking me to supply a
value for you know parameter b but what
i can do i can specify the name of the
parameter here the name of the third
parameter is c so i am simply going to
say c look at the intelligence again
it's showing that syntax as well for us
c :
then two and look at what happened in
the intelligence a kid has recognized
that we want to pass this value to see
so now obviously if I run this as you
might expect you know B is using its
default value whereas two is now passed
to the past as the argument for the
third parameter okay in our next video
we'll discuss making method parameters
optional by using optional attribute
that's present in system daughter on
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thank you for listening have a great day