Part 16 - C# Tutorial - Methods in c#.avi Video Lecture | C sharp: Enhance your Skills (English) - Back-End Programming

so welcome to prism technologies I am
rankled this is part 16 methods and
c-sharp in this session we will be
talking about the basic structure of a
method in c-sharp and the difference
between static and instance methods now
the first question is why methods why do
we need to use methods methods are
actually very useful because they allow
you to define your logic once and use it
at many places because of this they make
the maintenance of your application much
easier and methods are also called as
functions these terms are used
interchangeably if you look at a method
signature it has got several pieces in
that it has attributes access modifiers
written type method name parameters and
method body we will discuss about
attributes index modifiers in detail in
a later session return type the method
can have any valid written type it could
be any data type in c-sharp okay if you
don't want you method to return anything
then it can be void method name can be
any valid name except the reserved
keywords in c-sharp parameters you can
pass parameters to your method if you
don't want you know pass parameters
there again optional and obviously the
body contains any valid c-sharp
statements let's look at an example now
all this while you know we have been
writing all of a code in the within the
main method okay but it's also possible
that we can write our own method and
call it for example let us say I want
you to write a function you know which
can print even numbers okay it's very
easy to do for example let's write the
function okay as we discussed a function
will have attributes which are optional
we will talk about attributes in a later
session access modifiers we will talk
about access modifiers as well in a
later session but for now let's use the
public access modifier
now when we say the access modifier is
public then that means that method can
be called from anywhere okay there are
other types of access modifiers like
private protected internal protected
internal etc which we will be talking
about in a very great detail in a later
session now you can specify the return
type of your method after the access
modifier if you don't want your function
to return anything then you can specify
the return type is void void meaning the
method does not return anything back and
then the name of your function since we
are calculating even numbers here you
know maybe we will call this even
numbers function I don't want to pass
any parameters to this function so open
and close parentheses and then this is
the body of the function opening brace
and closing brace let's say I want to
plan the even numbers from 0 to 20 years
in this function so how do I do that so
we will declare a variable and start is
equal to 0 and while start is less than
or equal to 20 console.readline start
and then we need to increment start by 2
so if you look at this function this is
a pretty simple function you know which
will print even numbers ok now we define
the logic of calculating even numbers
ones and then we can call this function
anywhere we wanted ok let's say for
example I want to call this function in
my main method how do I do that ok I
need to create an instance ooh if you
look at this function this function and
this main function there is a slight
difference ok one difference is this
main method does not have an access
modifier we will have an access modifier
up
now another difference is this method
the even numbers method does not have a
static keyword in its declaration
whereas the main method has a static
keyword now this is one of the
differences between static methods and
see this method is called an instance
method whereas this method is called as
a static method okay now if I have to
invoke this method which means if I have
to call this method okay I have to use
an instance of this class this method
even numbers is present in program class
and since we don't have a static
modifier in the signature of this class
you know this method is called as an
instance method if you have a static
keyword then that method is called as a
static method okay so if you have to
invoke an instance method then you have
to create an instance of that class when
I say an instance it's nothing but an
object to the class in c-sharp the way
we create an object of the class is
using the new keyword so this method is
present in this class and this is an
instance method and to invoke that we
first have to create an instance of this
program class so program let's say P
equals new program so P is an object of
program class and now if I have to
invoke my even numbers class P dot even
numbers so that's one of the difference
between a static method and an instance
method if you have to invoke an instance
method you create an instance of that
class and on the instance of that class
you invoke this method using the dot
operator okay if I go ahead and run this
obviously it will print even numbers
from one till 20 now if I have to make
this method you know this is like an
instance method let's make this static
so in order to make this static how do
we do that just include the static
keyword public static void even number
so now this method is a static method
and look at this the moment I
type the static keyword here and when
this method has become the static method
we get a compiled Asian error okay even
numbers cannot be even programmed or
even numbers cannot be accessed with an
instance reference qualify it with the
type name instant okay so in which type
is this method present in a type called
program okay so if your method is a
static method then to invoke that method
you cannot do that on an instance of the
class instead you use the name of the
class classes you know so in this case
it's program since this is a static
method program dot even numbers so we
call it on the name of the class so now
again they would be the same except that
we made this static method now if we
look at this method we have the access
modifier we have the static modifier and
the return type and the name of the
method and we don't have any parameters
since we don't have any parameters
anyway we call this method it can only
print even numbers until 20 let's say we
want to give the flexibility for the
users to determine until what number
they want to print the even numbers you
know that flexibility you can provide by
passing in parameters let's say for
example I want to print even numbers
till 30 then if I pass 30 to this method
it should be able to print until 30 and
maybe in another program in another
application I want to print even numbers
till 50 then I pass in 50 instead of 30
but the logic remains the same except
that we want to enable the capability of
passing in parameters so it calculates
and returns even numbers back ok so
let's go ahead and see how to pass
parameters so to this method I want to
pass maybe we will call this target
until which target number okay so
instead of hard-coding
ok i want to print numbers till 20 i
want
the target so that's it now we have
passed this 30 for this one for this
target weighted parameter so it's going
to print numbers until 30 and if later
in my program I want to play until 50 I
can just call that method and pass 50
okay now if you look at this pyramid if
method it's not returning anything it's
just printing those values there let's
say for example I want to write another
method maybe an ADD method public and
the return type of the method in this
case is end and I'm going to call this
ad and first number comma n second
number so what should this method do
this this method should add those two
numbers and return their sum so return
first number plus second number so if
you look at this method this method is
actually taking in two parameters adding
them together and then returning the sum
back to the calling program to the
calling method so here the return type
of the method is integer here the return
type of the method is void now since I
don't have a static keyword in this
method this is an instance method and we
invoke this add method you cannot do it
on the name of the class you have to
create an instance of the class program
P equals new program P dot ad if you
look at the intelligence you know the
return type of this add method is
integer okay if you give it 10 comma 20
it's going to add those two numbers 10
plus 20 30 and then give back 30 to you
so 10 comma 20 so what's coming back and
integer is coming back so I can create a
variable and hold the result in this
variable so whatever this method returns
I'm storing that in this variable and
what else can you do
whatever if you want to print that you
can print if you want to save it to the
database you can do so consulate redline
sum is equal to slap that's it so this
program prints even numbers till 30 and
adds 10 plus 20 and prints that sum
which is 30 okay so we have seen the
signature you know the basic signature
of a method which consists of attributes
access modifiers written type written
type can be void and a method name any
valid method name and parameters which
are again optional and then method body
and we also have seen you know the
difference between static and instance
method when a method declaration
includes a static modifier that mean
that method is said to be a static
method otherwise it's called an instance
method if you want to invoke the static
method you do that on the name of the
class whereas if you have to invoke an
instance method you have to do that on
an instance of the class now what's the
basic difference actually there is a
reason why you makes it in methods and
some time feels and sir time a property
static and certain instance okay there
is a reason behind that we will be
talking about those in a very great
detail in a later session for now just
understand these two differences between
static instance methods and method is
said to be static if it contains static
keyword in its declaration otherwise
it's an instance method to invoke a
static method we have to do that on the
name of the class whereas an instance
method on the instance of the class it's
a compile time error to invoke an
instance method on the name of the class
and vice versa ok and later we will
actually talk about why we make certain
methods of static and certain methods as
instance methods we will see the logical
reasoning behind that in a later session
when we talk about classes for
additional resources you can visit these
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thank you for listening have a great day