OOPS Interview Questions and Answers | Object Oriented Programming Interview Questions C#

[@questpondvideos]

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[@digital.voyager]

C# 8.0 supports interface implementation methods, including default interface implementations, which allow you to add new members to a public interface without breaking existing implementers. I am little bit confused that why this change was made. @questpondvideos Could you please explain?

[@anshulasri152]

Answer to a question asked at last "Difference between abstract class with all abstract methods and and Interface" is that although both are technically similar but at the time of multiple inheritence abstract class fails, for multiple inheritance we have to implement Interface only. Also I would like to thank you for the video that explains concepts so easily with code examples!

[@adityapathak9999]

What is the meaning of "abstract class fails"

[@SHIVAML987]

@@adityapathak9999 That means we will have a compile time error. So, technically if we need some implemented + some abstract method then only go ahead with abstract class, otherwise, interfaces.

[@hassanadil3535]

That's true, but can't you go with multi level inheritance among classes and achieve the same.

[@svb651]

23:54 The Answer can be yes I think because compile-time polymorphism is achieved through method overloading and operator overloading, which do not require inheritance

[@nikhilkohirlyakaji]

This video has cleared my biggest confusion related to Encapsulation vs abstraction which I have been facing for over 5 years now. Thanks

[@dominiquez5643]

Master class! Wow 20+ years developing and at last somebody explain things in a simple concrete manner! This is an amazing run down on OOP techniques properly exlained to be used and to answer questions from anybody in IT! Love this video!

[@Anuj_sk]

How can we inherit the properties of base class from derived class without declaring the object of base class in main() . Can you explain the backend architecture of inheritance Simple and very tough interview questions of Microsoft for 40 lakh per annum question.... Pata sabko hai pura gyan koi kabhi kisi ko nhi deta.... Bataiye

[@jaym4358]

Wow. I did not even notice the 1 hour pass by. This is the best interview prep and the best video that explains OOP concepts by far! Thank you so much.

[@jaym4358]

I had 3 technical interviews today. One of them had very heavy questions on OOP concepts. The interviewer loved my answer about what an interface is, and even admitted that he had a hard time grasping the concept earlier in his career. I passed that interview thanks to this video. I am moving on to the third and final round.

[@Father_Of_Sudeera_Muthusinghe]

@@jaym4358 Congratulations!!!

[@pranav288]

@@jaym4358 How was the final round ?

[@vedantkulkarni5437]

One suggestion to viewers....don't skip this video just because you are using different language other than cs....it is one of the best video for oop with proper explanation

[@sridhargana155]

An abstract class allows you to create functionality that subclasses can implement or override. An interface only allows you to define functionality, not implement it. And whereas a class can extend only one abstract class, it can take advantage of multiple interfaces.

[@phelipepalte]

Another difference between abstract class and interface is you can't do a dependency injection with abstract class..

[@jestem-kses]

Latest version of c# allow interfaces to provide default implementation

[@bosegeorge1425]

​@@phelipepalte actually you can.

[@abhishek.eswarappa]

Having attended loads of interviews as a c# developer, i can conclude this is the best OOPS tutorial in an interview perspective. Pure GEM.

[@questpondvideos]

Really grateful for your feedback , thank you :)

[@Father_Of_Sudeera_Muthusinghe]

One thing to notice... When we are talking about method "overriding vs overloading", we should emphasize that method overriding is a runtime polymorphism and method overloading is a compile-time polymorphism. I guess it will be an expected answer in an interview. Finally, thanks for this interview question video. It helps me a lot to gain self-confidence before going to interviews.

[@shreyaspatil24]

Yes. Also we should talk about method signatures.

[@priyeshdubey40]

but here is the catch he also told that without inheritance polymorphism will not work but you see overloading case which is example of compile time polymorphism is not following the inheritance thing ..I think he confused little bit.😉

[@Father_Of_Sudeera_Muthusinghe]

@@priyeshdubey40 yup. U r right. In the comment section he has accepted the mistake. Anyway a great video.

[@gazalkaintura2605]

@@priyeshdubey40 exactly I thought the same thing

[@vinothrajendran858]

Sir, I have suggested your videos to nearly 20 people(my friends and colleagues) who were all trying for their next job and they found your videos really helpful. we are forever grateful. Thank you so much :) . And I will keep spreading your channel videos.

[@danyahsan3958]

did you get the job

[@lavanyaguniganti1444]

Sir, I have cleared my interview in reputed MNC just by going through your interview videos. thank you so much

[@rangababupolavarapu517]

Do you have more interview questions

[@questpondvideos]

@@rangababupolavarapu517 you can visit www.questpond.com/interview-questions---answers-tutorial/cid63 for interview Q&A videos

[@sunrise7442]

Best video's ive ever came across that explains concepts so easy. I followed the questions and enrolled on Udemy for the extra questions not covered here, and Cleared my first interview after 15min post interviewing I was called by HR that I got the Job🎉🎉 kudos to you Sir.

[@AashuKun]

You explained the OOP concepts so clearly in just one hour, something my professor couldn't make me understand in four years! Thank you so much!

[@mariahaamir171]

Its really underrated channel; I my opinion its by far the best. I am following Questpond since 7 years

[@hemantvitthal3732]

Aftter many year (10 years) search on google or youtube, I found best programming concept, What I exactly needed. Thank you @Questpond.

[@lekhrajawasthi8272]

Thank you shiv sir for this easiest explanation. Answer to that last question is that : Abstract can't help in multiple inheritance but the Interface can do the multiple inheritance. So in case of any modification to the requirement one can easily modify interface by implementing multiple inheritance.

[@stepbackandthink]

You have explained this far better than actual training videos.

[@seijumimurasakibara5516]

your dry wit coupled with your easy to understand explanations makes this video enjoyable to watch! thank you for this, i've finally understood the difference between abstraction and encapsulation and learned couple more things as well. Please keep up the good work!

[@questpondvideos]

Thank You :)

[@hassanadil3535]

Hi sir, referring to question # 21, you can actually write logic in an interface because C# 8 introduced 'Default Interface Methods' where you can write default logic for interface methods.

[@omarcollazo5011]

This is the best explanation of abstraction vs encapsulation that I've ever heard. Thank you, sir!

[@legendgattu]

Abstraction is exposing only whatever is necessary outside a class. Encapsulation is binding data and behaviour (methods) together.

[@hirajabeen9681]

I am here to recall my concepts and I have seen lots of material pdfs , YT vids and consult with books as well but this video I must say is so accurate and totally concise and delivers exactly what anyone need ! Much Appreciation for you ! Hatts off to your Efforts ! More Power To You ! @Questpond

[@questpondvideos]

Thank You 🙏

[@unknownfacts1197]

Multiple inheritance is what makes interface and abstract class differ from each other when they become technically similar

[@questpondvideos]

So right. Thats the only BIG technical difference

[@unknownfacts1197]

@@questpondvideos Thank you.. Your explanations are so good sir 👍

[@automationselenium1331]

By far the best video on C# interview I have seen on youtube, how one hour passed I have no idea, your way of teaching is amazing and I can watch your videos for hours...thank you and god bless you.

[@NiravPatel01]

Question 11: can polymorphism work without inheritance? Yes for static polymorphism No for dynamic polymorphism

[@swap2281997]

Exactly!

[@jankichalise904]

I always knew the theory part but when it comes to interview every interviewer was like what's the practical implementation of it and i really found the answer nowhere. thankyou so much for taking efforts and making an awesome video

[@raoadnan442]

Awesome way of describing. I have been searching OOP interview question answers but unable to find a great teacher like you. Hurrah.. now I have. Love from Pakistan. Keep doing this great job.

[@Carbv1]

Thank you! I’m so glad you’re showing real time coding examples while explaining each necessary details. I’m learning a lot from this video. I can’t wait to watch your other videos! Thank you!!!

[@suprabhat7582]

I have cleared interview by referring your videos. Thank you.

[@nalinikantadash8669]

An Interface contains methods which are by default abstract.But as an abstract class is a partially defined parent class so there is a possibility that it can contain both abstract methods as well as non abstract methods.This is the basic difference between an interface and an abstract class.

[@SSSALLJOBSPORTAL]

Wah!! What an explanation boss!! Crystal clear explanation... 🙌 really thank you🔥

[@PabloMartinezfr]

Best OOPS Interview Questions and Answers on KZbin!

[@EdisonSeas]

Great video, for understanding OOP concepts not just for C# but also any other language even if they don't support them, (like JavaScript). Pura vida!

[@natnaelhabtamu2799]

THIS is GOLD, you can easily follow up with any OOP language. thanks sir 🤗

[@panic_seller]

Very good video, never paid attention for 1 hour in a KZbin video

[@kingfisher3791]

What most anyone can say about this video, it is really awesome. After seeing this i come to know what the purpose of oops concepts

[@binayashrestha4131]

Best OOP explanation video in KZbin !

[@TyagiNushrat]

It helps me a lot to get refresh my knowledge after so many work experience, Thank you so much.🙂

[@gopavarapuguruprasad]

One of best video about oops concepts interview question and answers I come across. Please keep up good work sir👍.

[@naseerhussain5272]

This is the Best Explanation one could have asked for

[@udithaliyanage6375]

23:59 Compile time polymorphism can be achieved without inheritance. As an example Method overloading and operator overloading.

[@fernandod3510]

You have a real talent for education and clear explanation. Thank you for all you have given.

[@praveenrajubattula701]

Good video. Just 1 correction - interface can contain implementation, which was implemented in c#8.

[@ShankarV-te7le]

Simply superb explanation...thank you @Questpond.

[@shubhamgadre5796]

//while creating/designing the functions/properties, I am actually implementing abstraction. //What needs to be shown to public and what to keep private is Abstraction. //The Designing process of the Employee class is Abstraction. //The implementation of Employee class is Encapsulation, as we have wrapped up all the functions in //Validate() method. //That's how encapsulation implements abstraction. Am I right?? Time. 13:25

[@ankursahani8564]

Sir your explanation is very systematic. Sir please upload Question and answer for top 50 C programming coding Question for fresher interview.

[@theintuitivetruth]

For the answer to last query, Even though we write abstract class same as interface, but we cannot do multiple inheritance of the abstract class, whereas we can implement multiple interfaces.

[@ryuzaki6865]

Plus when we are implementing methods of an Interface we don't need to use the "override" keyword, whereas when we are implementing the abstract method of an abstract Class we need to use the "override" keyword.

[@hassanadil3535]

Hi sir, referring to your question difference between abstract class and interfaces, the difference is abstract is actually used to write a complete process in which base process might be the same but the corresponding processes might be different and those will be implemented by the derived class for example, I am going to write a process for calculating gratuity for two types of employees permanent and contractual and 1 years gratuity for both of them are 100% net pay and 60% net pay respectively, now calculating gratuity is the purpose but these two implementations will be provided by the derived classes and will be invoked by the abstract class's method. Interface is a means for bounding a class to must have a couple of properties or methods.

[@rajeshmacpant]

Excellent. This is such an easy refresher or explanation of OOPS concepts.

[@digital.voyager]

• An abstract class allows us to implement methods as well as make them abstract to be overridden by child classes. • Interface does not allow us to implement any method we can only define its signature. • Any class can inherit only one abstract class but it can inherit multiple interfaces. Although, C# 8.0 supports interface implementation methods, including default interface implementations, which allow you to add new members to a public interface without breaking existing implementers. I am little bit confused that why this change was made. @questpondvideos Could you please explain?

[@10yearsago84]

Really a great set of questions. Thoroughly covered all the topics. Thank you sir :)

[@AzeemRaavi]

Awesome way to answers the OOP questions. Love from Pakistan 🇵🇰

[@ahmadcomputeracademy7344]

Parent class is also called super class or base class. Child class is also called derived class... Some interviewer asked this question. So I decided to comment here down for such amazing video.

[@gametechtutorial4670]

Best video so far. Clear, right at the point. Im getting the point right away. Thank you for sharing the knowledge sir.😃🙇‍♂

[@DuI41093]

Sir answer to the final question is Multiple inheritance cannot be achieved using the Abstract class, but multiple inheritance can achieve using the Interface

[@shubhampanwar7647]

very very detailed and good quality video. i watched till question 27

[@AhmedAdel-xg1cm]

Very intuitive and clear explanation of the concepts , thanks a lot for sharing. hope u will make a video for solid principles

[@husnainmazhar6739]

amazing video,, cleared all the concepts.. Thanks

[@vidyamahathi6057]

I got a job.I just watched this video for oops concepts 😁

[@MrMcKnite]

Happy for you mate

[@trijay]

For the last question here are my few cents, When abstract class have all abstract methods then what is the difference between abstract class and an interface? 1) Here abstract class inherit only one other class 2)Where as Interface can inherit multiple interfaces 3) Abstract classes can have properties and constructor 4)Interface cannot have any property or constructor Please correct me if I am wrong

[@mohamedmusthafa1057]

I find this Channel You saved My lot of time thanks ❤

[@benedictmabanga5736]

Best explanations! Thank you for this🙏🙌

[@MrRajatbhatt]

Sir as you have mentioned polymorphism can't be implemented without inheritance. However static polymorphism aka method overloading we can do it in the same class. So for me saying polymorphism can't be implemented without inheritance seems contradictory. Please advice

[@questpondvideos]

Yeah you caught me :-) and you are perfectly right. A object polymorphism ( Dynamic polymorphism) needs inheritance. Missed that word dynamic , thanks for correcting. Do send a message to [e-mail] , would like to give you 8 months of subscription on Questpond. Happy learning.

[@aneeshrajr2418]

@@questpondvideos Thankyou Sir for make this clear....

[@aneeshrajr2418]

👍

[@shabanashaik2784]

@@questpondvideos can I also get it?? I too had the same doubt and checked the comments and i found this...

[@judycariaga3945]

You really great at explaining it. Now I understand the OOP more. Thank you so much. ♥️

[@sadakagaja]

Awesome sir It helping me to learn C#❤️

[@sandeepsingh3588]

i think in abstarction there should be one thing should be mentioned like it can be achived by abstract class and interface while in encapsulation it can be achived by access modifiers and also they both have hide complexity but abstraction managed it as high level and encapsulation do it in low level

[@shivamsoni4215]

Thank you for making simple topic complicated ♥

[@keshavt6982]

Keep up the great work. Explanation was super easy to understand

[@reshmabegampathan395]

Thank you for sharing these with us with practical. Really. We can grasp easily with practical. My ans to ur question: In abstract class, there is non abstract methods also so we don’t have to implement that, only we need to implement abstract methods but in interface, all things we need to implement forcefully. Please tell me this is right or wrong. Once again, thank you so much. Keep going.

[@vaibhavraj581]

Very intuitive and clear explanation of the concepts , thanks a lot for sharing. Looking forward to learn more from your videos.

[@Devdumplings]

This is the best one compared any oops languages. Having come from a different language background finally I understood what exactly the concepts clearly and thanks for being realistic about the preparation importance as I was a unprepared hero 😂

[@saravanansangeetha1206]

Very very useful video for us, appreciate your efforts

[@manpreet.mg16]

You have done great video short and ans to remember in easiest way

[@cjimenez2581]

in Q11: I can implement it using interfaces... This is java, but I guess we can do the same on c# interface Shape { void draw(); } class Circle implements Shape { @Override public void draw() { System.out.println("Drawing a circle"); } } class Square implements Shape { @Override public void draw() { System.out.println("Drawing a square"); } } public class Main { public static void main(String[] args) { Shape circle = new Circle(); Shape square = new Square(); drawShape(circle); drawShape(square); } public static void drawShape(Shape shape) { shape.draw(); } }

[@aumganeshbhaihadiyal5168]

2 main differences between Abstract class and Interface 1. Abstract class can have a default constructor Interface cant have constructors 2. Abstract class cant achieve multiple inheritance Interface can achieve multiple inheritance

[@akashgupta2971]

Huge respect for the efforts and time that you and your team have put, the sequence of the questions were very connecting and gradual... Now I have a better concept after watching the video... And for the question you asked at the end of the video... My answer is that abstract classes can be partially or not implemented whereas interfaces should be fully implemented.

[@yosiosibemekun2785]

An interface only allows you to define functionality, not implement it.

[@akashgupta2971]

@@yosiosibemekun2785 yeah that's another difference

[@nithunandhugaming6519]

No one cant explain this much easier in overriding and virtual keyword concepts

[@shivangisingh9920]

You are awesome... Helped me a lot in the interview.

[@deepz513]

thank you sir, along with deeply explaining the concepts you are valuable advised is much appriciated.

[@godwinchalz4863]

best video for oops in C#

[@phanirao2008]

wonderful, very crispy, specially example taken easy than domian specific

[@MilindKTechnology]

24:38 Inheritance is not must for polymorphism as you can implement static polymorphism without inheritance. Please let me know sir if you had a different mean.

[@CALLMEMANISH82]

thanks, very beneficial video to revise oop concepts.

[@yogeshindurkar2981]

Q. 11 Can polymorphism work without inheritance. Ans : Yes Static polymorphism is also a polymorphism and it can be achieve without inheritance. Please correct me if I am wrong.

[@yogeshkumar_29]

You are Best Sir !! Really very helpful

[@avantikamishra7586]

hi explanation is awesome and you did great efforts in compiling all stuff in one place. Thanks please provide ebook of questions

[@manjuanoop7239]

Excellent material thanks for sharing such an informative video👍🏻

[@izmar47]

Thank you for the lesson. I can't tell you how much this helped. I appreciate your effort. Liked and Subscribed!

[@hiteshdogra3047]

In response to your question "How an Abstract Class with all abstract functions is different from and Interface?", I guess Even if Abstract class has all the functions defined as abstract, the child class is not forced to override (Or provide functionality of) the abstract functions. Whereas in case of Interface implementation the implementing class has to provide all the implementations of all the functions. Am I correct?

[@MarkRyanAlot]

You're right. One key difference between the two is that an interface can only have public properties and methods, while an abstract class is the same as a regular class that can have variables, properties, and implemented methods using different access modifiers. An abstract class can have both abstract and virtual methods. Also, if you want to leverage IOC you will be using interfaces instead of abstract classes.

[@anysdev]

This is not correct. You must implement the functionality for abstract methods just as you would with the interface methods so as far as implementation requirements go there is no difference (note that he marked them as abstract methods, not virtual methods, so they must be overridden). The main difference in that situation is simply that a class can only inherit from a single abstract class but can implement multiple interfaces. Conceptually you can figure out when to use which one. For example if you have a Cat class and a Dog class, it makes sense for them to inherit from an abstract Animal class because both of them are actually animals and all animals will have some shared functionality like breathing. However a ClimbsTrees abstract class wouldn't really make sense, it's more of an indication of what some animals can do rather than what they are, so in this case you can use an IClimbTrees interface and apply it to any animals that can climb trees. Now the dog doesn't need to care about anything to do with climbing trees but the cat can inherit the interface and add the functionality.

[@abdulhai_007]

No bro, U can't have definition of abstract method within abstract class. U can just simply DECLARE(not Define) a method as abstract method. But yes, if u want to define(means,give implementation) a method within abstract class, u need to make it as virtual, And in that case it's not mandatory to override it by its child class.

[@priyeshdubey40]

You told that without inheritance polymorphism will not work but you need to see overloading case which is example of compile time polymorphism which is not following the inheritance thing ..

[@abdullahahmed8468]

amazing content with clear and simple answers, Thanks alot

[@CodingPathshalaa]

Sir at 24:35 you said for polymorphism inheritance is must , but since we do overloading in only one class , we dont need inheritance for Static polymorphism.

[@akshaysoren5400]

Thank you so much sir. i really like the way you explain.

[@sanobarmemon1113]

Method overloading can be achieved without inheritance. Hence polymorphism can be implemented without inheritance.

[@justiceeziefule9308]

This is well explained. Thank you bro

[@kishanpatel6657]

Very good point to point.

[@praphulshresth]

Excellent work guru ji, maja hi aa gya. or videos banayeeye python par

[@nagaboddu852]

Thank you sir , it’s very useful 😊

[@priyanshu4016]

last question ans: we can implement the multiple inheritances using interface but not with an abstract class that make difference between abstract class with all abreact method and interface. Please correct me if my understanding is wrong sir.