Part 64 - C# Tutorial - How and where are indexers used in .net Video Lecture

though welcome to precision technologies
I invented this is part 64 of c-sharp
tutorial in this video we'll discuss
about where our index is used in dotnet
framework and what our index URLs in our
next video session will discuss about
creating indexes if you're an asp.net
web application developer then you must
be familiar with session state and
application state variables to store a
retrieve data from session state or
application state variables we use index
URLs
let's understand this with an example
let's flip to visual studio here I have
an asp.net web application project and I
am on the code-behind file of webform
one dot aspx now within the code-behind
file in the page load event let's say I
want to store something into session
state variable then I can make use of
the session object and look at this the
moment I open the square bracket I can
see that there are two indexes defined
on the session object the first index R
here R is an integral in the exa and
then once I press the down arrow I can
see that there is another index R and
this is a string index ax the fact that
we have two indexes on this you know
session object indicates that it's
possible to overload indexes
the disk is about overloading indexers
in a later video session all right now
let's say I want to store something into
the session object and let's say I want
to use the string index ax and let's use
the key session 1 and then I want to
store you know a string stating session
1 data into the session object with that
key now let's say I want to store
another string and let's call the
session to data and this time the key is
going to be session 2 now here we are
using the index R to actually store the
data into the session object now is it
possible to retrieve data using indexes
absolutely let's see how to retrieve
data out of these you know session keys
so obviously to print something on to
the waveform I have to use the response
object so response dot right now let's
print out a hard-coded string saying
that session 1
is equal to now to retrieve the data out
of the session object look at this I'm
going to use the session object and then
I open the square bracket and then it
shows me again that I have an integral
indexer and a string index R now let's
actually use the integral index L to
retrieve the data out of the first
session Kay
okay so I'm going to say is zero as the
index okay
so zero index is going to pull the data
that is present in the first session key
session one and then look at that the
session object actually returns an
object data type because you can store
anything into a session state so it
returns an object but we know that it's
a string so I'm going to convert that to
a string all right now let's write an
HTML break so that the output comes in a
separate line and then let's say I want
to retrieve a session I mean the data
that's present in the session variable
with key session two now here you know
the to retrieve data from the first
session key by using an integral indexer
here let's say I want to use the string
index ax so I just use the double quotes
and then specify our session key which
is session 2 and let's change this
hard-coded string here to session 2 data
now let me go ahead and run this as you
might expect we should be able to
retrieve data from both the keys session
1 and session 2 to retrieve data out of
session 1p we are using the integral
index ax and for session 2 we are
actually using the string index ax so
this is one classical example where
indexes are used in dotnet framework
okay now if you interact actually see
the you know those indexes within that
class look at this this session is
actually a property within the page
object so I'll right click on the
session and go to definition so this is
the session property and this actually
returning an HTTP session state object
so when we right-click on that and then
go to definition within that class you
should see two indexes now we usually
create indexers using this keyword look
at that I
to indexers here the first one is the
integral indexer and the second one is
the string index ax now don't worry
about the syntax of the indexers here
we're going to discuss about creating
indexers in our next video session now
if you look at this index I look at that
it has got a get and set accessor as
well just like properties in the
Exeter's have get and set accessories
discuss about creating indexes in detail
in our next video session now so we have
just seen the metadata of httpsession
state class showing those two indexes
integral indexer and a string index R
now let's look at another example of you
know indexes usage in dotnet framework
now most of us have written a D or
dotnet code now let's say for example
here I have this TBL employee table
I want to retrieve data from this table
and write that on a webform okay so
obviously we need to write some ad or
dotnet code and just to speed things up
you know I do discussing about the area
dot net code is out of the scope of this
video we discussed about ad or dotnet in
a separate video series video dotnet
video tutorial for beginners please
watch videos from that series okay but
then let me copy this area dotnet code
here and then let's go to the code
behind file of this web form and let's
paste that within the page load event so
let's delete whatever that's there all
today and let's paste this so we are
using the configuration manager class to
read the connection string from web
config file so in the web config file I
have already a connection string with
the name DB CS database connection
string there so we are reading that
connection string from web config file
using the configuration manager class
and using the connection string be a
building of a sequel connection object
and look at our sequel command select
star from TBL employee we are executing
the command which is going to return a
sequel data reader object and look at
this we are looping through each row
that we retrieved from the database and
look at this
each row will have these columns
employee ID name gender and city but
let's say I want to print out the
employee ID and the name of every
employee onto the web
form then there are you know two ways
that I can retrieve the employee ID
column value okay so let's say for
example you know de-spawn start right
now the first row will be retrieved in
to the reader object so I can use reader
and then look at this the moment I open
the square bracket I can either use the
integral indexer on the reader object to
retrieve the column value or I can use
the name now let's say for example if I
say a reader of zero I'm using the
integral indexer meaning I want the
first column value the first column is
employee ID so we will be getting the
employee ID okay so the reader of 0.2
strength so that should return employee
ID and just you know let's hard-coded
string here saying ID is equal to you
know whatever is the employee ID that we
get and then maybe I want a space and
then let's say we want to print the name
as well so response dot right and let's
say name is equal to plus I want to
retrieve the name out of the reader
object again I can either use the
integral indexer or the string index I
if you are using the string the string
index ax then you specify the name of
the column let's say for example I want
name of the employee then I say reader
of name that because that's the name of
the column dot to string and then let's
write an HTML break so that every
employee record comes in a separate row
alright let's go ahead and run the snap
as you might expect we should be able to
print employee ID and the employee name
look at that employee ID is equal to one
name is equal to MA we get that for all
the eleven employees now again here
we're using the integral index and the
string index ax so it's you know in
dotnet framework there are several
classes that already use these indexers
now in our next video session will
discuss about creating indexes for our
own class for example let's say I have a
class called company which is going to
return employees now is it possible to
retrieve the company employees using
indexers just like how we are using
indexers to retrieve the column values
and session values absolutely we'll
discuss about that in our next video
session but now you know here we have
used the sequel data reader and then we
know that it has got two indexes let's
quickly inspect the metadata of the
sequel data reader class to see if they
if it has the two indexer so we are in
sequel data reader class and then look
at that I have two indexers here again
you know integral indexer and a string
index a-- all right so that's the
metadata which is showing the indexer so
from the above example so what are
indexes in c-sharp from both examples
that we have seen you know it should be
very clear that indexes allow instances
of classes to be indexed but just like
arrays in our next video session we will
discuss about creating indexes on this
slide you can find resources for a speed
on a c-sharp and zequals away interview
questions that's it for today thank you
for listening have a great day