Part 37 - C# Tutorial - Delegates usage in c#.avi Video Lecture - C sharp

Oh welcome to presume technologies I am
venket this is part 37 delegates usage
in c-sharp past 36 we had introduction
to delegates in that part we have seen
the basics of delegates and the basics
index how to create a delegate make it
to point to a function and then by
invoking the delegate it will
automatically invoke the function it is
pointing to and we understood that
delegates are types a function pointers
meaning the signature of the delegate
should match the signature function it's
pointing to in this part we'll look at
an example of how to use delegates okay
and they by look at the flexibility that
delegates provide us with okay so we
look at an example and this part will be
completely demos so let's slip back to
visual studio now let's say I have a
class called employee and this class has
got some properties like the ID of the
employee name of the employee etc so
let's have the auto implemented
properties with default get in set
accessors similarly this class is going
to have name and obviously name of the
employee is string type and then salary
which is integer and experience okay now
what I want this I want a method in this
class called promote employees and what
should this method do it should take in
a list of employees and then based on
some logic it should print the names of
the employee who is who are eligible for
promotion okay so let's look at the
class let's say public white is the
written type and then let's call the
method as promote employee
and then this is going to take in a list
of employees now the list class is
actually part of genetics namespace so
we have to import that so using system
dot collections dot genetics so list of
this is going to take in a list of
employees so let's say employee list and
then loop through that list for each
employee and our employee list okay so
for each employee within our employee
list let's say for example you know if
the employees experience is more than
five years then probably we want to
promote them so what we will do is if
you know the logic to promote employee
is that if the employee salary is
greater than not salary if the employee
experience is greater than five years
then he is eligible for promotion so
let's print out his name so if that
employee and his experience is greater
than or equal to five which means five
years then this employee is eligible for
promotion so let's say console.writeline
where is that employee his name promoted
okay so we have the simple method to
promote employees now this class I want
to make this class reusable okay anybody
should be able to reuse and provide
their own logic of promoting employees
but if you look at this class here this
is not reusable that's because you have
hard-coded the logic of how you want to
promote employees okay let's say for
example there is a company Y which wants
to promote employees based on maybe
their salary for example if anybody who
has greater than 10,000
as salary they want to promote that can
they reuse your class without modifying
it they can't they have to change this
logic here and maybe some other
companies ed has another set of
different criteria to promote employees
so your class now is not reusable you
have hard-coded that logic ok so I want
to have this promote employees method
but then it has to be flexible enough
for people to plug in the logic they
want to promote their employees ok so we
look at that in the next part but let's
complete this in the session now let's
say I want to use this class what we do
we create a list of employees so I will
say list of employee let's say EMP list
is equal to new list of employees and
then we need to add some employees to
this list so we will say EMP list dot
add and to this list we need to add a
new employee so we will say new employee
and let's say we have got some employees
like
maybe ID is equal to one zero one name
is equal to maybe and maybe his salary
or salary is equal to five thousand and
experience is equal to five years okay
so we have this employee here let's add
some and sample employees let's say Mary
and then this guy is going to be Mike
and maybe his salary is four thousand
rupees and he has got let's say four
years of experience and this is John who
has six thousand salary and six years of
experience three thousand and this guy
let's say has got three years of
experience let's say this guy is Todd
okay look at this we have four different
employees and two of them have
experienced greater than or equal to
five okay so if we want to use our
method we can go ahead and use that
for the moment let's make this method a
static method so we can invoke that
method without creating an instance of
employee class so now to use that all I
can do is employee dot promote employees
and then we can pass our Employee List
okay now if we go ahead and run this
people who have five years of experience
greater than or equal to five years
should be promoted who has more than
five mary and john so mary and john
promoted now this is not delegate we
haven't used delegates at all in this
program and that's why this program is
not that flexible now tomorrow if
somebody wants to promote their
employees based on let's say their
salary or their experience or some other
criteria then they have to come here and
change you know this promote employee
method which is bad okay because our
employee class we decided that we want
that to be reusable
okay anybody any logic they should be
able to plug into this promote employees
and then without modifying this class
this method they should be able to reuse
that how is it possible with the help of
delegates which we will be looking at in
an action in the next demo okay but try
and remember that these delegates are
extensively used by framework developers
you know to plug the logic the
developers want to into the framework
methods okay so in the next demo we'll
go ahead and see how to make this class
how to make this employee class reusable
so that end users I mean so that
developers who uses your class in
methods within that can plug in their
logic without there having to modify
your class and that's what is the
flexibility that delegates provides us
with so if you want to pass a method as
a parameter to another method then
probably we can make use of delegates
and that's what we'll be looking at in
the next session alright that's it for
this session thank you for listening
have a great day