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Constructors in C#.NET Part 1 | C#.NET Tutorial | Mr. Bangar Raju — Transcript

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0:02[Music]
0:07welcome to Nares technologist I'm bangar
0:09Raju and in this video uh I will
0:12demonstrate about
0:15Constructors so what is this Constructor
0:19see objectoriented programming is all
0:22about writing the code inside classes we
0:25just going to write the code inside a
0:27class and a class is a collect of
0:30various members like Fields methods
0:33Constructors etc etc and in that one of
0:36the most important member that is
0:38present in a class is going to be called
0:40as a Constructor so what is a
0:42Constructor means it is a special method
0:46present under a class responsible for
0:53initializing the variables of that class
1:00responsible for initializing the
1:02variables of that class so it's a
1:03special method present under a class
1:05responsible for initializing the
1:06variables of that
1:08class okay and now the main importance
1:12of a Constructor is it is responsible to
1:15initialize the variables inside your
1:17class what is that we'll talk on it just
1:19a minute meanwhile if it is a method it
1:21requires a name now and remember the
1:25name of a Constructor method the name of
1:28a Constructor method
1:31is exactly the same name of the class in
1:37which it was
1:40present the name of a Constructor method
1:43is exactly the same name of the class in
1:45which it was present so we can't change
1:47this thing now so if your class name is
1:49test your Constructor name is test if
1:50your class name is demo your Constructor
1:52name is demo you cannot change it and
1:55another important thing is and moreover
1:58it's a non
2:01value wring method it's a non-value
2:04wring method Constructor methods doesn't
2:06require written any value that doesn't
2:09written any value so just generally
2:11methods are two types value wring non
2:13value wring but Constructors are purely
2:15nonv value wring they never written any
2:18value and next each and every class
2:22requires this
2:25Constructor if we want to create
2:30the
2:31instance of that
2:34class this is another important Point
2:37each and every class requires this
2:38Constructor if we want to create the
2:40instance of that class if at all we want
2:43to create the instance of that
2:44particular class make sure your class
2:47contains a Constructor if I don't have a
2:49Constructor if you don't have a
2:50Constructor we cannot create the
2:52instance of the class but when I tell
2:55this point you'll be having a doubt what
2:57is the doubt earlier you might be
3:00writing classes and in the classes you
3:03may not Define anything called as
3:05Constructor but still you are able to
3:06create the instances of those classes
3:08something like this you defined a class
3:10like this class
3:11test in this class I'm declaring a
3:14variable called as in I something like
3:17this and now let us somewhere I want to
3:21create the instance of this class test
3:23obj is equals to new test create the
3:26instance of the class so is this
3:29statement Val valid yes it is valid we
3:31can create the instance but what the
3:33last point is telling here each and
3:34every class requires this Constructor if
3:36we want to create the instance of the
3:38class but here we are creating the
3:40instance but we don't have anything
3:41called as Constructor and if this is
3:45valid the last Point what we are talking
3:47here doesn't make any sense why without
3:51that Constructor we are telling instance
3:52cannot be created and here we don't have
3:55a Constructor but still we are able to
3:57create the instance so this will be a
3:59out what everyone will have in the mind
4:02so let me clarify that what is it it's
4:06the
4:08responsibility of a programmer to define
4:11a
4:13Constructor under his class it is the
4:16responsibility of a programmer to define
4:18a Constructor under his class
4:22and if he fails to do so on behalf of
4:28the programmer on behalf of the
4:31programmer an
4:33implicit
4:35Constructor gets defined in that class
4:41by the
4:44compiler on behalf of the programmer an
4:47implicit Constructor gets defined in
4:49that class by the compiler actually we
4:52need to do it but we did not do it if
4:54you don't do that on behalf of us the
4:58compiler will Define an implicit
5:00Constructor into that class so what
5:02happens you know this class after
5:06compilation this class after compilation
5:09will contain one implicit Constructor
5:11like this how
5:13public
5:15test and remember the name is test why
5:19the name is test because the Constructor
5:21name should exactly be the class name
5:23class name is test so the Constructor
5:25name is also test and inside this what
5:27will be present you know I is equals to
5:30Z what is that initializing the variable
5:34initializing the variable so why is the
5:37variable getting initialized here that
5:39is the responsibility of the Constructor
5:41that is the first point we're talking
5:43it's a special method present under a
5:45class responsible for initializing the
5:47variables of that class so if a class
5:50variable is initialized implicitly means
5:53that is done by a Constructor that is
5:55why every variable you declare directly
5:58under the class or every field you
6:00declare directly under a class has a
6:02default value if you don't give all
6:05numeric types are initialized with zeros
6:08and Boolean types are initialized with
6:10false string and object types are
6:11initialized with null means see in this
6:15I'm also going to declare a string
6:17string s did not initialize bull b did
6:20not initialize and now all the things
6:22will come here also string s and bulby
6:27but remember inside this Con structor
6:30all these are initialized s is equals to
6:32default value
6:34null and B is equals to default value
6:38false so like this the initialization is
6:42performed for each and every variable
6:45that is the role of the Constructor that
6:46is why Constructor is very important for
6:50us inside a class and if you don't have
6:53this Constructor with these variables
6:56will not be initialized because without
6:58we assigning a value a value coming
7:01there means there's not a magic show so
7:03someone has to assign the value here so
7:05who is going to do that the Constructor
7:08will do that and this Constructor is not
7:09defined by aember we did not Define The
7:12Constructor who defined this Constructor
7:14the compiler defined this Constructor
7:17for us and we call this as a implicit
7:20Constructor that is a Constructor that
7:22is implicitly defined and if we Define
7:25the same thing that is called as
7:26explicit Constructor if at all we are
7:29going to Define this Constructor
7:30explicitly we call that as a explicit
7:33Constructor okay otherwise every
7:35Constructor is going to be an implicit
7:37Constructor so you till now you might be
7:40defining 100 classes in all the 100
7:43classes you never defined a Constructor
7:46but still all those classes contain a
7:49Constructor and all those class
7:51Constructors are defined by the compiler
7:53for us and some few important points to
7:56remember here Point number one
8:03implicit
8:05Constructors implicitly defined
8:10Constructors
8:13Constructors are also known as default
8:19Constructors are also known as default
8:23Constructors why actually default
8:25Constructor means a Constructor which
8:28doesn't take any parameter see already
8:32on the top I said a point Constructor is
8:35a special method and why I'm just
8:38pointing this right now here is see
8:40method because of the method you can
8:43pass parameters to Method also there is
8:45a chance to pass
8:46parameters and if you pass any
8:48parameters to the particular thing the
8:50Constructor will become parameterized
8:52and right now there are no parameters so
8:54this is a parameterless Constructor this
8:57is going to be a parameterless
8:58Constructor so every parameterless
9:02Constructor will initialize the
9:04variables of the class with default
9:06values so that's
9:08way implicit Constructors are
9:11parameterless and parameterless
9:13Constructors are also known as default
9:16Constructor so let me change the
9:18definition implicitly defined
9:20Constructors
9:22are
9:24parameterless these Constructors are
9:27also known as default constu
9:29Constructors implicitly defined defined
9:34Constructors are parameterless and these
9:38Constructors are also known as default
9:40Constructors the first important point
9:42if a Constructor is implicitly defined
9:45don't forget that is parameterless and
9:48if it is parameterless they can Al they
9:51can also be called as default
9:53Constructors Point number two implicitly
9:56defined Constructors
10:00are
10:01public the constructors which are
10:03defined implicitly are public you notice
10:06said this class is a normal class here
10:09but when I defined the Constructor when
10:10I just said the Constructor gets defined
10:13I have mentioned here as a public why
10:16because implicitly defined Constructors
10:18are public they are going to be public
10:20Constructors here okay and another
10:25thing we can also Define a Constructor
10:29under the class we can also Define a
10:33Constructor under the class and if we
10:36Define it and if we Define it we can
10:41call it as explicit Constructor explicit
10:45Constructor and
10:49explicit
10:51Constructor and an explicit Constructor
10:54can be
10:57parameterless or
11:00parameterized also an explicit
11:03Constructor can be parameterless or
11:06parameterized but implicit Constructors
11:08cannot be parameterized implicit
11:11Constructors are
11:12parameterless but explicit Constructors
11:15can be parameterless or parameterized
11:17also two options are there for us both
11:19can be done okay fine let's just take a
11:23small example and define a Constructor
11:25okay here I've taken a project called as
11:27demo project in this I have class called
11:29program in this program class I wanted
11:32to define or I wanted to just declare a
11:35variable in I equals
11:38to uh or in
11:41simple okay
11:43next uh bub bu B there two
11:48variables now let me come here create
11:51the instance of the class program p is
11:54equals to new
11:56program and once after creating the
11:58instance of the
12:00class console do right
12:05line P do I the variable name is i p do
12:10I trying to print the I value as well as
12:14the B value also so one more time I'm
12:17writing P do
12:22B console do R
12:26line and do remember we did not assign
12:29any value for I and B but still when you
12:32run the code it prints
12:35values you can notice still you can see
12:39the values printed over there what are
12:41the values zero and F but don't forget
12:44we did not assign any value here we did
12:47not assign any value here and that value
12:51what has coming over there is a given by
12:54is given by The Constructor which
12:56Constructor implicit Constructor and we
12:59don't require to give that
13:03value uh let's just print this message a
13:06little bit clear what is it value of I
13:14is
13:18plus and value of B
13:22is plus so it's going to print both the
13:26two values for us
13:31okay so value of I is zero and the value
13:34of B is false it's just going to print
13:36the two values for us so that's what
13:38even if we did not assign any values you
13:41are able to see the value for I and B
13:44how the value came now the value came
13:47through the Constructor we did not
13:49assign so internally this class contains
13:53one implicit Constructor and that
13:55implicit Constructor is going to
13:58initialize the variables
14:00okay so can I define these Constructors
14:02explicitly you can Define how can I
14:04define a Constructor explicitly if you
14:06want to define a Constructor explicitly
14:09this is the syntax to define a
14:11Constructor
14:13modifiers
14:14name parameter
14:17list and write here so this is the
14:20syntax your modifiers name parameter
14:24list and then you're going to write your
14:26statements here so let us try defining a
14:29Constructor on our own now so right now
14:32we used an implicit Constructor here and
14:34that implicit Constructor is helping us
14:37in creating the instance and
14:38initializing the variables and you can
14:40Define this Constructors explicitly also
14:43how to define let's open the solution
14:48Explorer add a new class here
14:53add a
14:54class I'll name the class
14:57as X
14:59explicit con demo explicit Constructor
15:02demo simply call it as explicit con
15:06demo now in this class I want to write a
15:10Constructor no
15:11public explicit cond
15:14demo so this is an explicit Constructor
15:17what I defined inside this class public
15:20explicit condo this is an explicit
15:22Constructor okay and this Constructor if
15:26you don't Define also there'll be but
15:28implicit now it is explicit and here I'm
15:30writing a simple
15:31code console dot right
15:35line Constructor is called now
15:40static void
15:42main create the instance
15:46now explicit cond demo obj is equals to
15:50new explicit con demo creating the
15:54instance now we are creating the
15:57instance of the class now okay
15:59and afterwards console.
16:04rline and
16:05remember we are creating an instance and
16:09whenever you create an instance there
16:11will be a call to the Constructor there
16:14will be a call to the
16:19Constructor and I I can prove you this
16:22like this you can
16:25watch Constructor is called how many
16:28times times you create the instance that
16:31many number of times the Constructor
16:34will be called for
16:36you suppose I'm creating three instances
16:40obj1 obj2
16:42obj3 and you watch it every time you
16:45create the instance it will call the
16:48Constructor
16:50so if you notice the previous
16:53program in the previous program we did
16:56not Define any Constructor explicitly so
16:59the Constructor is implicit okay so
17:02right now I'm going to create the
17:04instance when I create the instance now
17:08even though the Constructor is implicit
17:09a call to the Constructor will take
17:11place so what is going to happen now it
17:13is going to call the implicit
17:14Constructor now and that implicit
17:17Constructor is now going to initialize
17:19the variables which variables I and B
17:22which zero and false so the point to
17:25understand is whenever the instance of a
17:28class is created
17:30then there is a implicit call to the
17:33appropriate Constructor why we are going
17:35to make the appropriate point this
17:37instance creation will call the
17:39Constructor okay means actually I should
17:42not use the word implicit here why I
17:44should call explicit only why because we
17:47are calling the Constructor explicitly
17:49where are we calling
17:52Watch program P what is program you can
17:55see there it is a class present under
17:58the demo project namespace it is a class
18:01present under the demo project
18:03namespace now come here when I say
18:05program and put my mouse here it is not
18:07showing you class what is it showing you
18:10program. program what is program.
18:12program the first program is a class and
18:15the second program is your Constructor
18:17means you are calling the Constructor
18:21explicitly you are calling the
18:23Constructor explicitly we are explicitly
18:26making a call to the Constructor and
18:29when we call the Constructor the
18:31implicit Constructor is called and will
18:34initialize the
18:36variables and coming here here also the
18:38same thing only you
18:41notice you notice this is your class
18:44name and this is your Constructor name
18:47and if you debbag you'll understand much
18:49better place a breako here by using F9
18:53so let us place a breakpoint here by
18:55using F9 and run the code
18:59watch when you added a breako over there
19:03when you added a break point the control
19:06will go and stop on that line when the
19:08execution is taking place just a second
19:11uh the control will come and stop on
19:13that particular line when you just over
19:15for executing the code now the control
19:18stopped on the line now press F1 now if
19:21you press F1 see what is going to happen
19:24so right now the control is on this line
19:26which line explicit con demo obj is
19:29equals to if you press
19:32F1 you see the control jumping to the
19:37Constructor the control jump to the
19:39Constructor now and after the control
19:41jump to the Constructor now it is
19:43executing the code inside the
19:45Constructor and coming back next again
19:50you're calling the sorry creating the
19:52second instance again goes to
19:54Constructor call again executes the
19:57logic comes back
19:59again third instance going to
20:01Constructor executing the logic and
20:04coming out of this so like this whenever
20:08the instance of any class is created the
20:12call is explicitly made to the
20:16Constructor here a point will be
20:19confusing for you a little bit what is
20:22it defining second one
20:26calling what is defining what is calling
20:29defining a Constructor
20:32means implementing one Constructor in
20:35your class so this is called defining
20:38this is called defining means we are
20:39explicitly writing the code for the
20:41appropriate thing that's called
20:43defining defining can be two types what
20:47implicit or explicit what is that
20:51implicit or explicit either you define
20:55it otherwise compiler will define it but
20:59calling what is calling whenever we the
21:02instance we are calling the Constructor
21:04calling is
21:07explicit you only should call implicit
21:10calling will not take place defining
21:12will be implicit but calling must be
21:14done explicitly if you don't call the
21:17Constructor explicitly that is not going
21:20to execute that may be an implicit
21:22Constructor or that may be an explicit
21:25Constructor but calling should be done
21:27explicitly by us if you explicitly call
21:30only the Constructor which is defined
21:32implicitly or which is defined
21:34explicitly will execute so this is the
21:38basic information for us about a
21:40Constructor okay uh in the next video I
21:43will just demonstrate about the various
21:45types of Constructors that are present
21:47in a class and how to work out with them
21:50thank you for watching the video for
21:51more videos please subscribe to our
21:53YouTube channel Nares it
21:57[Music]
21:58h
21:59[Music]

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