Part 66 - C# Tutorial - Overloading indexers in c# Video Lecture | C sharp: Enhance your Skills (English) - Back-End Programming

so welcome to presume technologies I am
venket this is part 66 of c-sharp
tutorial in this video we'll discuss
about overloading indexers please watch
part 64 and 65 before proceeding with
this video we'll be working with the
example that we started in part 65 now
if you remember in part 65 we
implemented an indexer that has an
integer parameter notice this indexes
that we implemented it's accepting
employee ID as its parameter for the
given employee ID this indexer is going
to return their name
similarly this indexer can also be used
to change the employee name for example
let's flip to this waveform 1 here we
are creating an instance of the company
class which has this index ax now let's
say within this company I want to
retrieve the name of an employee whose
ID is 2 then all I need to do is pass
number 2 to the indexer and look at the
return type of this index 8 string
meaning it's going to return the name of
that employee now if I want to change
the name of this employee to mark all I
need to do is set that name like this so
this piece of code is going to change
the name of this employee with ID is
equal to 2 - mark ok now at the moment
this company class has got only one
index ax and it's taking one parameter
which is of type integer
now remember methods can be overloaded
based on the number and type of
parameters similarly indexers can also
be overloaded based on the number and
type of parameters at the moment our
class has one index ax and this index ER
has an integer parameter okay now let me
copy this and paste this piece of code
here now if you look at these two
indexes they are identical meaning both
of these indexes are having only one
parameter and both of these parameters
are of type integer so obviously when I
compile this project I'm going to get an
error look at the error type demo dot
company all it defines a member called
at this which is nothing but the indexer
with
same parameter types so the parameter
type is the same thing so I'm going to
get a compiler error because you cannot
have indexers with the same number and
type of parameters multiple indexers
that's not possible
now on the other hand I can have
something like this into maybe age now
if I build this look at that will I get
a compiler error notice on the status
bar will succeeded now I don't get a
compiler error why because you know
though this is an integer parameter I
have another parameter here so that's
how you know when I actually try to use
these indexes look at this when we flip
to the waveform and let's say company
and then when I open the square bracket
notice that it shows there are two
indexes the first index takes only one
parameter of type integer and then if I
click on this you know down arrow look
at that it shows the other index ax
which has got two parameters okay so
basically to distinguish between which
indexes we want to invoke you know you
can only overload indexes based on the
number and type of parameters now let's
say I want to implement another indexer
here which is going to return the total
number of employees by gender for
example you know let's in my company I
go off at the moment we have you know
eight employees here okay now out of
these eight employees if you look at the
female employees there one two and three
there are three female employees and
five male employees now what I want to
do is something like this I should be
able to print the total number of male
employees so response dot write total
male employees is equal to now I want to
use the indexer you know on this company
object and pass gender to it
okay and this index ax should return the
total number of employees to me now look
at this I have a red squiggly here you
know showing that as an error because at
the moment this company doesn't have any
indexer that takes string parameter okay
so let's go ahead and implement
something like this okay and to do that
what I'm going to do
so here we have an indexer so let's get
rid of these two parameters and let's
pass in a string parameter and of type
gender okay so I mean gender is the name
of the parameter so basically what we
want to do we want to you know when I
pass in gender you know something like
male here I want to get the list of the
count of all male employees within the
company okay so what are we passing here
male so what I'm going to do here are
from this list I'm going to use a link
function called count so within the list
we are invoking the count function so
for each employee within that list if
that employee gender matches with what
we are passing again so what are we
passing for example on our web form if
you look at our web form we are passing
male so when male is passed it will
check okay is the passed in gender male
matches with the employee gender within
this list if yes then you know it's
going on count all those employees whose
gender matches and it's going to return
that back now look at the return type of
this count function it's an integer okay
but what is the return type of our our
index it's string so let's convert this
to string using the to string method so
that's what get accessor now what else I
want to do I also want to implement the
set access our meaning I want to change
the gender of employees for example you
know something like this if I say
company of male so I want to change the
gender of all male employees to maybe
something like this female is this
possible absolutely so you know all the
male employees gender change it to
female okay so let's implement the set
accessor for our indexer so here what we
are passing in we are passing in gender
so what I'm going to do here now I'm
going to loop through each employee
object so for each
employee in the list employees if the
employee dot gender is equal to the
gender
so here what we are passing to the
indexer we are passing in mail so we are
looping through each employee if the
gender of that employee matches with
mail which is passed in then what we
want to do we want to set that employee
gender to whatever value that we are
setting it to so here what is the value
that we are assigning female so the male
employees gender is female because this
value is going to receive whatever you
assign after equal to so we are changing
the gender to female okay so we have the
indexer here now let's actually make
some changes to properly test this code
so this line is going to print total
male employees and let's also print the
total female employees so for that we
need to pass female here and this one is
going to be before update so response
dot right before update and then let's
print an HTML break so that the output
comes in a separate line all right so
let's copy this and then have another
HTML break let's have to HTML breaks
here and then look at what we are doing
here this line you know before update if
you remember within our company we've
got five female I mean five male
employees and three female employees so
obviously these two lines should I mean
this line should print three male
employees and this line should print you
know the number of female employees
which is five female I mean female
employees are three and male employees
are five and then here we are changing
the gender of male employees to female
so after this line is executed the
number of total number of male employees
will be zero but total number of female
employees will be eight so let's copy
these two lines and then
pace them there so we are basically
printing the total number of male and
female employees before and after
updates so let's copy this line so this
line is going to change the gender of
male employees to female and let's call
this after update and then let's have an
HTML break after that okay so these
changes let's go ahead and run so
obviously in the wave form renders you
know the first two lines should print
you know the number of male employee
look at that total male employees 5
that's before update okay and total
female employees three but after update
look at that total male employees is
zero and total female employees is eight
okay so we are able to you know change
the gender of the employees using this
indexer and using this indexer you know
when we pass mayor you know here it's
going to invoke the get accessor of our
indexer that takes a string parameter
okay and this is going to return you
know all the employees whose gender is
male for this piece of line okay and
this line is going to invoke the set
accessor of this indexer that takes the
string parameter alright so in this
video we have seen how to overload
indexes based on the number and type of
parameters on this slide you can find
resources for asp.net c-sharp and
sequence of interview questions that's
it for today thank you for listening
have a great day